Fix WinPS adapter tests

[SteveL-MSFT]

PR Summary

Pester 5.7.1 was crashing due to stdout leaking from BeforeAll. Fix is to redirect the native command output to $null. In addition, modified test to be skipped if not Windows or not elevated. Removed nested use of BeforeDiscovery within tests.

After resolving the crash, apparently many tests have been broken for some time but wasn't reported since Pester crashes before it writes the output file so CI thinks they all passed:

• Split WinPS cache and non-cache tests into separate files since there's some interaction with messing with the cache and paths that cause subsequent non-cache specific tests to fail
• Add more tracing to help isolate issues including emitting current working directory for resource since on my system dsc kept using the store installed version instead of the debug built one
• In BeforeAll section, isolate PATH and PSModulePath to use specific resources so that ones already on the system don't get used
• Fix PSCredential handling in WinPS adapter where classbased returns type as PSCredential instead of [PSCredential]
• Change PSCredential test to use a class based resource instead of mocks for end-to-end validation
• Add trap in adapter so that any uncaught exceptions get traced
• Fix issue where adapters weren't being added to internal resource list so on discovery, it finds older version of adapters
• Fix test checking if [console] is available before using as in CI it's not available
• Skip rebootPending tests if not Windows or elevated