System.IO.FileSystem.AccessControl tests leave behind files ACL'ed to be difficult to delete

[MattGal]

https://github.com/dotnet/runtime/blob/master/src/libraries/System.IO.FileSystem.AccessControl/tests/FileSystemAclExtensionsTests.cs#L475

In checking out some helix machines, I found various leftovers from these tests, some of which result in creating files and directories which are specific deny-acl'ed for all users.

Ideally any changes done like this could be cleaned up via a finally() block, since if a real user runs these tests locally their personal temp folder could be clogged up with the same.

[ViktorHofer]

cc @carlossanlop @jozkee

[danmoseley]

This could potentially be done in TempDirectory itself -- when it fails to do the delete it attempts to fix the ACL's recursively

runtime/src/libraries/Common/tests/System/IO/TempDirectory.cs

Line 46 in 1923bba

catch { /* Ignore exceptions on disposal paths */ }

That way it would help all tests that use it.