[Feature] Add test for speculative_token_map

[Achazwl]

Motivation

Add test for #3822.

Modifications

Add a class TestEAGLEEngineTokenMap in test/srt/test_eagle_infer.py.

Checklist

• Format your code according to the Code Formatting with Pre-Commit.
• Add unit tests as outlined in the Running Unit Tests.
• Update documentation / docstrings / example tutorials as needed, according to Writing Documentation.
• Provide throughput / latency benchmark results and accuracy evaluation results as needed, according to Benchmark and Profiling and Accuracy Results.
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