Print active filters in Detailed/Diagnostic output

[fflaten]

1. General summary of the pull request

This PR enables Pester to print enabled filters during a run when using Detailed or Diagnostic output level.
The filters are shown at the start of discovery. Example:

Discovery: Starting test discovery in 2 test containers.

Starting discovery in 2 files.
Filter 'Tag' set to ('Function').
Filter 'ExcludeTag' set to ('Ignore', 'Stuff').
Filter 'Line' set to ('C:\tests\file1.Tests.ps1:37', 'C:\tests\file12.Tests.ps1:371').
Discovery: Discovering tests in /workspaces/Pester/demo.ps1
Discovering in /workspaces/Pester/demo.ps1.
Found 3 tests. 13ms
Discovery: Found 3 tests in 17 ms
Discovery: Processing discovery result objects, to set root, parents, filters etc.
Filter: ('Set-BuildRunToCI' Unit Tests) There is 'Ignore, Stuff' exclude tag filter.
...

Known issue: It might be confusing to the user that filters are shown before "Found 3 tests" as that number is before processing/filtering. Moving the output after that message would require invoking a new plugin-step in Discover-Test

Fix #1721