[Tests] Fixing bug inside MultiModalProfiler.

[shenoyvvarun]

Purpose

This only adds tests as the fix is addressed as part of #21798

This PR fixes the issue #21344 where large image requests hangs in vllm waiting for the request to timeout.
Bug: MultiModalProfiler counts only patch tokens but, there are other bookeeping tokens like tile_seperator, image_start, image_end tokens in the input. This causes the encoder_budget to be slightly lower the actual budget. Whenever an image that uses all tiles is sent, VLLM accept the request but, scheduler can never schedule it because there is not enough encoder budget. Silent issue and No error is produced

Test Plan

1. Large image ( 4k x 4k) - LLama Guard 4
2. Full Context length Text + Large image + Llama Guard 4
3. Sanity test with (7k x 4k Image)

Test Result

1. Large image ( 4k x 4k)

{
    "id": "chatcmpl-464e45d8a7834c41aa96b93c388f5be6",
    "object": "chat.completion",
    "created": 1753798054,
    "model": "vllm-model",
    "choices": [
        {
            "index": 0,
            "message": {
                "role": "assistant",
                "content": "\n\nsafe",
                "refusal": null,
                "annotations": null,
                "audio": null,
                "function_call": null,
                "tool_calls": [],
                "reasoning_content": null
            },
            "logprobs": null,
            "finish_reason": "stop",
            "stop_reason": null
        }
    ],
    "service_tier": null,
    "system_fingerprint": null,
    "usage": {
        "prompt_tokens": 2669,
        "total_tokens": 2672,
        "completion_tokens": 3,
        "prompt_tokens_details": null
    },
    "prompt_logprobs": null,
    "kv_transfer_params": null
}

2. Full Context length Text + Large image (2467 is the encoder budget)

{
    "id": "chatcmpl-9406bb1facd54ea194a270fed2577ca8",
    "object": "chat.completion",
    "created": 1753798730,
    "model": "vllm-model",
    "choices": [
        {
            "index": 0,
            "message": {
                "role": "assistant",
                "content": "0",
                "refusal": null,
                "annotations": null,
                "audio": null,
                "function_call": null,
                "tool_calls": [],
                "reasoning_content": null
            },
            "logprobs": null,
            "finish_reason": "stop",
            "stop_reason": 200001
        }
    ],
    "service_tier": null,
    "system_fingerprint": null,
    "usage": {
        "prompt_tokens": 131069,
        "total_tokens": 131071,
        "completion_tokens": 2,
        "prompt_tokens_details": null
    },
    "prompt_logprobs": null,
    "kv_transfer_params": null
}

3. Sanity Test

curl http: //localhost:8000/v1/chat/completions \
    -H "Content-Type: application/json" \
    -d '{
    "messages": [
        {
            "role": "user",
            "content": [
                {
                    "type": "image_url",
                    "image_url": {
                        "url": "https://upload.wikimedia.org/wikipedia/commons/8/85/Portas_da_Cidade%2C_Ponta_Delgada%2C_isla_de_San_Miguel%2C_Azores%2C_Portugal%2C_2020-07-29%2C_DD_123-125_HDR.jpg"
                    }
                },
                {
                    "type": "text",
                    "text": "Describe this image in detail and also specify where this can be found."
                }
            ]
        }
    ],
    "model": "vllm"
}'
{
    "id": "chatcmpl-86908cb63b644decbcfcbc63d26fbb36",
    "object": "chat.completion",
    "created": 1753799599,
    "model": "vllm",
    "choices": [
        {
            "index": 0,
            "message": {
                "role": "assistant",
                "content": "The image depicts a large, ornate archway in the center of a city square at dusk. The archway is made of stone and features two large arches with a decorative top section. It is illuminated by purple lights on either side.\n\nHere are the main points describing the image:\n\n* **Archway**\n\t+ Made of stone\n\t+ Features two large arches\n\t+ Decorative top section with a crown-like design\n\t+ Illuminated by purple lights on either side\n* **City Square**\n\t+ Located in front of the archway\n\t+ Features a statue in the center\n\t+ Surrounded by buildings on all sides\n\t+ Streetlights and cars visible\n* **Buildings**\n\t+ White with brown trim\n\t+ Feature arched windows and doors\n\t+ Have balconies on the second floor\n\t+ Appear to be old and historic\n* **Statue**\n\t+ Located in the center of the square\n\t+ Depicts a person standing on a pedestal\n\t+ Not clearly visible due to distance\n* **Streetlights and Cars**\n\t+ Streetlights line the square and surrounding streets\n\t+ Cars are parked along the streets and driving through the area\n\t+ Traffic lights visible in the distance\n* **Sky**\n\t+ Dark blue and cloudy\n\t+ Indicates that it is dusk or evening\n\nIn summary, the image shows a beautiful and historic archway in a city square, surrounded by old buildings and a statue. The archway is illuminated by purple lights, and the square is bustling with streetlights and cars. The dark blue sky suggests that it is dusk or evening. \n\nThis archway can be found in Horta, Faial, Azores, Portugal. The archway is known as the Portão da Cidade (City Gate) and is a iconic landmark in Horta.",
                "refusal": null,
                "annotations": null,
                "audio": null,
                "function_call": null,
                "tool_calls": [],
                "reasoning_content": null
            },
            "logprobs": null,
            "finish_reason": "stop",
            "stop_reason": null
        }
    ],
    "service_tier": null,
    "system_fingerprint": null,
    "usage": {
        "prompt_tokens": 2346,
        "total_tokens": 2732,
        "completion_tokens": 386,
        "prompt_tokens_details": null
    },
    "prompt_logprobs": null,
    "kv_transfer_params": null
}

(Optional) Documentation Update

[gemini-code-assist]

Code Review

This PR fixes a critical bug in the MultiModalProfiler that caused hangs with large image requests. The fix involves using the length parameter on PlaceHolderRange for accurate token budget calculation. A new test suite has been added to validate the fix. I've identified a high-severity issue in the test file related to incorrect token calculation, which needs to be addressed.

[DarkLight1337]

See my comments in #21798

[DarkLight1337]

Maybe you can add the tests while the other author focuses on the fix itself

[github-actions]

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🚀

[shenoyvvarun]

Maybe you can add the tests while the other author focuses on the fix itself

Makes sense 👍

[DarkLight1337]

Can you fix pre-commit?

[DarkLight1337]

Thanks, LGTM given tests pass

[shenoyvvarun]

Can you fix pre-commit?

Fixed. Please note that the failure now is not due to changes in the PR, but, due to file below. I will rebase and check if that fixes the issue.

docs/design/fused_moe_modular_kernel.md

[DarkLight1337]

No need to rebase, I can force-merge