Tests - Unskip the three tests gated on $env:APPVEYOR

[andreasjordan]

Follow-up to #10521.

AppVeyor the service is gone, but tests/gha.shim.ps1 sets $env:APPVEYOR so the ported appveyor.*.ps1 harness keeps working. A side effect: three skip conditions written for the old AppVeyor image are now permanently true on the Azure fleet, and have been silently skipping ever since the move — on runners the reasons were never assessed against.

Test	Lane	Recorded reason for the skip
Get-DbaWindowsLog.Tests.ps1 (whole IntegrationTests Describe)	SINGLE	"the command finds the error log through a SQL Server startup event in the Windows Application log, and the CI runners have nothing to parse"
Enable-DbaFilestream.Tests.ps1 ("FileStream Level to 2")	RESTART	"the instance does not support FileStream Level 2"
Add-DbaComputerCertificate.Tests.ps1 ("PFX certificate with chain")	default	none recorded

Why these are worth re-checking rather than left alone

The Get-DbaWindowsLog reason in particular looks likely to have expired. Its VMs now boot from a sysprepped golden image and start the instance on first boot, which writes exactly the SQL Server startup event the command parses — plus Repair-GhaSqlServerName restarts the engine when the image carries a stale @@SERVERNAME. That is a different situation from the old hosted image the comment describes.

The other two are genuinely unknown. The filestream reason is a property of the instance, and nothing in .github/runners/image-scripts/ configures FILESTREAM either way. The certificate one never recorded a reason at all.

Evidence so far

All three pass against a live lab (SQL03/SQL04), including the parts CI skips:

Get-DbaWindowsLog.Tests.ps1            Passed   1 passed, 0 failed, 0 skipped
Add-DbaComputerCertificate.Tests.ps1   Passed   6 passed, 0 failed, 0 skipped
Enable-DbaFilestream.Tests.ps1         Passed   3 passed, 0 failed, 0 skipped

That establishes the tests are sound, not that the runners will satisfy them — the skips are environmental. This PR is how we find out: CI scopes tests from the changed files, so these three run on the real image.

If CI disagrees

The recorded reasons are kept as comments rather than deleted, so re-skipping is cheap. If one fails, please re-skip that one on a condition describing the actual missing precondition rather than on $env:APPVEYOR — the point of this change is that gating on a dead CI provider hides which environments a test really needs.

🤖 Generated with Claude Code

[potatoqualitee]

shit wait, @claude why didn't the tests trigger for andreas?

[potatoqualitee]

ahh outage 🙄

[potatoqualitee]

reinited and real failures unfortuantely