VS Code: fix repo name resolution cache

[valerybugakov]

• Ensures the repo name resolution is cached and we don't make unexpected API calls for already resolved remote URLs.
• This fix is critical for enterprise clients because the regression significantly increases the repo-name resolution latency, which is used by every enterprise client with Cody Context filters and is on the critical path for every autocomplete request. In my local tests, it adds ~500-600ms to every repo name resolution call.
• Slack thread with more technical details.
• Closes https://linear.app/sourcegraph/issue/CODY-4139/investigate-repo-name-resolution-latency-increase

Test plan

CI with updated unit tests.

Changelog

• Context Filters: fixed repo name resolution cache.

[valerybugakov]

This new test fails if shouldCountRefs is set to true in getRepoNameCached.

[dominiccooney]

Good work although the subtlety of this scares me about observables in general.

Is this covered by tests that changing auth will re-query for repo IDs?

You mentioned an LRU, but that is not here... Any concerns about this being a source of leaks?

[valerybugakov]

Good work although the subtlety of this scares me about observables in general.

Same! It's easy to make this mistake. Similar to concerns about React's useMemo sensitivity but even subtler.

Is this covered by tests that changing auth will re-query for repo IDs?

I don't know if we have this type of test for all the features where reactivity was introduced. We should start adding more of those. I tested this case manually with a debugger for now.

You mentioned an LRU, but that is not here... Any concerns about this being a source of leaks?

The LRU cache was added to vscode/src/repository/repo-name-resolver.ts to replace regular objects. This change should keep those caches from growing forever.