[CI/Build] Split out MM pooling tests

[DarkLight1337]

Purpose

Run MM extended pooling tests separate from MM extended 1 to speed up CI

Test Plan

Test Result

---

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request refactors the multi-modal model tests in the CI configuration by splitting the extended tests into 'generation' and 'pooling' suites. This improves granularity and clarity of the test jobs. The changes in .buildkite/test-amd.yaml and .buildkite/test_areas/models_multimodal.yaml correctly partition the test runs and update dependencies. However, I've noticed a potentially critical oversight in the new 'pooling' test jobs where a dependency installation seems to be missing. Please see my detailed comments.