testing: TempDir RemoveAll cleanup failures with "The process cannot access the file because it is being used by another process." [1.18 backport]

[gopherbot]

@ianlancetaylor requested issue #51442 to be considered for backport to the next 1.18 minor release.

@gopherbot Please open backport to 1.18.

At least one person is encountering this problem in 1.18. There are workarounds but they are awkward. The fix would be harder to backport to earlier releases.

[gopherbot]

Change https://go.dev/cl/407877 mentions this issue: [release-branch.go1.18] testing: include ERROR_SHARING_VIOLATION in Windows cleanup retries

[bhasden]

Out of curiosity, what causes some items to be included in a release and some items to be deferred?