Add some documentation for System.Threading.Lock APIs

[kouvel]

Summary

• Added some documentation for the Lock and Lock+Scope types and their APIs
• Depends on Remove RequiresPreviewFeatures attribute on Lock, add test using the lock keyword runtime#102222
  • Removed the RequiresPreviewFeatures attribute on Lock, the relevant code change is in that PR

[gewarren]

Thanks for adding these.

[kouvel]

Thanks! I believe I've address all of the feedback, also adjusted a couple of things in the latest commit.

[learn-build-service-prod]

Learn Build status updates of commit 14dee1b:

✅ Validation status: passed

File	Status	Preview URL	Details
snippets/csharp/System.Threading/Lock/Overview/Project.csproj	✅Succeeded
snippets/csharp/System.Threading/Lock/Overview/UsagePatterns.cs	✅Succeeded	View
xml/System.Threading/Lock.xml	✅Succeeded	View
xml/System.Threading/Lock+Scope.xml	✅Succeeded	View

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[learn-build-service-prod]

Learn Build status updates of commit 6d46e61:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Threading/Lock.xml	✅Succeeded	View
xml/System.Threading/Lock+Scope.xml	✅Succeeded	View

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel