fix(cache): separate package cache by platform

[Sahitya0805]

Description

Previously cache keys did not include platform, causing packages from different platforms to overwrite each other.

This PR stores cached packages under cache/pkgs/<platform>/<package>.

Fixes #1014

How Has This Been Tested?

• Added test_cache_key_display in cache_key.rs to verify that CacheKey correctly prepends the platform folder.
• Ran cargo test -p rattler_cache and cargo check locally.

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.
    Tools: Custom AI Assistant

Checklist:

• I have performed a self-review of my own code
• I have added sufficient tests to cover my changes.

[baszalmstra]

This doesnt integrate the functionality anywhere and when you do add that its important to think about a migration strategy for people with existing caches.

[ritankarsaha]

This doesnt integrate the functionality anywhere and when you do add that its important to think about a migration strategy for people with existing caches.

Ahh I see the PR here, but I think you have left a comment here mentioning that #2165 is incomplete and doesn't fix the issue, also both addresses different issue tags. Can you look into #2167 once to see if everything is addresses properly over there ?

[baszalmstra]

This commit says remove duplication but this actually adds a lot of duplication..

[Sahitya0805]

Thanks for pointing that out!

You're right the cache path resolution logic is currently duplicated. I'll refactor it by introducing a helper function to resolve the cache path (handling both the new platform aware layout and the legacy layout) and update the PR accordingly.

[baszalmstra]

Are you still working on this? There is another PR in #2167 trying to solve the same issue. If you are not working on this PR it might be nice for the author of that PR to continue?

[Sahitya0805]

Yes, I'm still working on it. I'll address the duplication issue and push an update shortly.
If PR #2167 already covers everything needed, I'm also happy to close this PR.

[Sahitya0805]

Thanks for the review!

I refactored the cache path resolution logic into a helper function to remove duplication and updated the call sites accordingly. I also removed the redundant assignments and verified that all tests pass locally, including test_cross_platform_package_cache.

Please let me know if any further changes are needed.