[analyzer] Fix cache size counter drift in EvictingFileByteStore._cleanUpFolder

[vedant21-oss]

Problem

EvictingFileByteStore._cleanUpFolder was decrementing currentSizeBytes unconditionally,
even when file.deleteSync() threw an exception:

try {
  file.deleteSync();
} catch (_) {}
currentSizeBytes -= fileStatMap[file]!.size; // <- always runs, even on failure

If a file cannot be deleted (e.g. due to a permissions error or a race with another process),
the counter is decremented as though the deletion succeeded. This causes the cache to
underestimate its own size, which can prevent the eviction loop from running again even
though the cache is still over its maxSizeBytes limit.

Fix

Move the decrement inside the try block so it only executes when the deletion actually succeeds:

try {
  file.deleteSync();
  currentSizeBytes -= fileStatMap[file]!.size; // <- only runs on success
} catch (_) {}

Tests

Two regression tests are added to a new EvictingFileByteStoreCleanUpTest class:

• test_cleanUpFolder_successfulDeletion_decrementsSizeCounter - basic happy-path eviction.
• • test_cleanUpFolder_failedDeletion_doesNotDecrementSizeCounter - simulates a failed
• deletion by revoking chmod 000 on the parent directory and verifies that the files
• remain on disk (i.e. the loop is not fooled by a corrupted size counter). Skipped on Windows.
  Fixes Analyzer cache size accounting drift in EvictingFileByteStore #63118

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[vedant21-oss]

@google-cla check

[vedant21-oss]

Submitted a fix in #63127 — moves the currentSizeBytes decrement inside the try block so it's only decremented when deletion actually succeeds.

[copybara-service]

Thank you for your contribution! This project uses Gerrit for code reviews. Your pull request has automatically been converted into a code review at:

https://dart-review.googlesource.com/c/sdk/+/494021

Please wait for a developer to review your code review at the above link; you can speed up the review if you sign into Gerrit and manually add a reviewer that has recently worked on the relevant code. See CONTRIBUTING.md to learn how to upload changes to Gerrit directly.

Additional commits pushed to this PR will update both the PR and the corresponding Gerrit CL. After the review is complete on the CL, your reviewer will merge the CL (automatically closing this PR).