[CI] Enable cache for virtual env and parallelize pytest via xdist

[LeiWang1999]

as title.

[github-actions]

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[gemini-code-assist]

Summary of Changes

Hello @LeiWang1999, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request, despite its title suggesting CI improvements like virtual environment caching and pytest parallelization, primarily introduces a significant change to the TileLangThreadSyncPlanner in C++ to enhance memory access conflict detection. It also includes minor, seemingly unrelated, modifications to Python files. The discrepancy between the stated intent and the actual changes warrants further investigation.

Highlights

• Discrepancy between PR intent and changes: The pull request title and description indicate an intent to enable virtual environment caching and parallelize pytest runs for CI. However, the actual code changes provided do not reflect these stated goals and instead modify core logic in C++ and Python files unrelated to CI.
• Core logic modification in src/transform/thread_storage_sync.cc: Introduced a new range_is_overlap boolean variable and associated logic within the TileLangThreadSyncPlanner class. This change refines the conflict detection mechanism for thread storage synchronization by proving whether memory access ranges overlap using analyzer_.CanProve and then using this new boolean to determine if buffers are in conflict.
• Minor Python file changes: A minor typo (d appended to destroy_model_parallel) was introduced in examples/bitnet-1.58b/vllm_workspace/conftest.py. Additionally, a blank line was removed from tilelang/engine/phase.py.

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[gemini-code-assist]

Code Review

This pull request's title and description suggest CI/CD improvements, but the code changes seem unrelated, focusing instead on compiler logic and fixing a typo. Please consider updating the PR title and description to accurately reflect the contents.

I've identified a critical syntax error in conftest.py that needs to be fixed. Additionally, I've provided a few suggestions for the C++ code in thread_storage_sync.cc to improve its readability and maintainability. Please take a look at my comments.

[gemini-code-assist]

The logic here can be simplified by combining the two CanProve calls into a single condition. This makes the code more concise and easier to understand.

        range_is_overlap =
            !(analyzer_.CanProve(prev_indice < curr_indice || prev_indice > curr_indice,
                                 arith::ProofStrength::kSymbolicBound));

[gemini-code-assist]

This comment restates what the following line of code does. The code return range_is_overlap; is self-explanatory, and the preceding comment provides enough context. It's best to avoid comments that simply mirror the code's logic.

[challenger0004]

Hey