Change temp folder name used in installer tests (#45523)

Change temp folder name used in installer tests (#45523)

Tests in the AppHost.Bundle.Tests assembly seem to randomly fail due to a race condition
with the file system. They try to create separate '0','1','2'... subdirectories to isolate
the published files for each test, but I think what's happening is that files may be
marked for deletion, but then not deleted until a later write. For instance, files in
'2' may be marked for deletion and some may fail a File.Exists check, which leads to
'2' being recreated, at which point deletion may occur, which will cause the current test
to fail due to a concurrent write operation.

This change tries to avoid locking & contention by randomly generating folder names and
using a (hopefully atomically created) lock file to indicate ownership of a particular name.

Fixes #43316