test: Load new model version should not reload loaded existing model version(s)

[kthui]

What does the PR do?

Add the following tests on model version reload:

1. If a version is loaded and unmodified, then it should not be reloaded on the next load request.
2. If a version is loaded but modified, then it should be reloaded on the next load request.
3. If a version is not loaded and its model file is in the model directory, then it should be loaded on the next load request.
4. If a version is not loaded nor its model file is in the model directory, then it should be loaded on the next load request.
5. If a generic file is modified on the model directory, i.e. model_directory/common_dependency.py, then all loaded version(s) should be reloaded on the next load request.

Checklist

• PR title reflects the change and is of format <commit_type>: <Title>
• Changes are described in the pull request.
• Related issues are referenced.
• Populated github labels field
• Added test plan and verified test passes.
• Verified that the PR passes existing CI.
• Verified copyright is correct on all changed files.
• Added succinct git squash message before merging ref.
• All template sections are filled out.
• Optional: Additional screenshots for behavior/output changes with before/after.

Commit Type:

Check the conventional commit type
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• build
• ci
• docs
• feat
• fix
• perf
• refactor
• revert
• style
• test

Related PRs:

triton-inference-server/core#388

Where should the reviewer start?

Start with the core PR.

Test plan:

The PR adds the test, see the Test plan on the core PR.

• CI Pipeline ID: 17511909 17650341

Caveats:

N/A

Background

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Related Issues: (use one of the action keywords Closes / Fixes / Resolves / Relates to)

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[rmccorm4]

Non-blocking for this release, but curious about this comment: https://github.com/triton-inference-server/server/pull/7527/files#r1722556601