Add CulturedConditionalFactAttribute and CulturedConditionalTheoryAttribute to XUnitV3Extensions

[Copilot]

Adds conditional variants of CulturedFactAttribute and CulturedTheoryAttribute that support CalleeType and ConditionMemberNames, matching the pattern of the existing ConditionalFact/ConditionalTheory attributes.

These derive from CulturedFactAttribute/CulturedTheoryAttribute (xunit v3 only) and use the existing ConditionalTestDiscoverer.EvaluateSkipConditions to set Skip at construction time.

• New attributes in Microsoft.DotNet.XUnitV3Extensions/src/:
  • CulturedConditionalFactAttribute — extends CulturedFactAttribute
  • CulturedConditionalTheoryAttribute — extends CulturedTheoryAttribute
• Tests in CulturedConditionalAttributeTests.cs: skip state validation, property exposure (CalleeType, ConditionMemberNames, Cultures), theory data passthrough, culture verification via CultureInfo.CurrentCulture

[CulturedConditionalFact(new[] { "en-US", "fr-FR" }, typeof(MyTests), nameof(IsSupported))]
public void RunsPerCultureWhenConditionMet() { }

[CulturedConditionalTheory(new[] { "en-US", "ja-JP" }, typeof(MyTests), nameof(IsSupported))]
[InlineData(42)]
public void TheoryRunsPerCultureWhenConditionMet(int value) { }

To double check:

• The right tests are in and the right validation has happened. Guidance: https://github.com/dotnet/arcade/blob/main/Documentation/Validation.md

[Copilot]

Pull request overview

Adds xUnit v3 cultured conditional test attributes so tests can combine culture-specific execution with existing conditional skip evaluation.

Changes:

• Adds CulturedConditionalFactAttribute.
• Adds CulturedConditionalTheoryAttribute.
• Adds tests validating skip behavior, exposed properties, theory data passthrough, and culture selection.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/Microsoft.DotNet.XUnitV3Extensions/src/CulturedConditionalFactAttribute.cs	Adds the cultured conditional fact attribute implementation.
src/Microsoft.DotNet.XUnitV3Extensions/src/CulturedConditionalTheoryAttribute.cs	Adds the cultured conditional theory attribute implementation.
src/Microsoft.DotNet.XUnitV3Extensions/tests/CulturedConditionalAttributeTests.cs	Adds xUnit v3 tests covering the new attributes.

[akoeplinger]

@AndriySvyryd won't this potentially cause issues if the tests run concurrently with other tests and the process culture is changed?

[AndriySvyryd]

That would be an issue in XUnit.
https://github.com/xunit/xunit/blob/main/src/xunit.v3.core/ObjectModel/CulturedXunitTestCase.cs#L103 sets it globally, but in V2 it was set only for a specific thread:
https://github.com/xunit/xunit/blob/main/src/xunit.v2.tests/TestUtility/CultureAwareTesting/CulturedXunitTestCase.cs#L53
This looks like a deliberate change, so there must be some mechanism to isolate the other tests.
@bradwilson Would you like to weigh it?