Annotate ErrorUtilities methods for nullable analysis

[rainersigwald]

For instance,

https://github.com/microsoft/msbuild/blob/00781ad1353afba25451148dba61845ac139b572/src/Shared/ErrorUtilities.cs#L54-L60

Should have [DoesNotReturn]

https://github.com/microsoft/msbuild/blob/00781ad1353afba25451148dba61845ac139b572/src/Shared/ErrorUtilities.cs#L110-L116

should have [NotNull] on parameter (see second sense in the NotNullAttribute docs)

https://github.com/microsoft/msbuild/blob/00781ad1353afba25451148dba61845ac139b572/src/Shared/ErrorUtilities.cs#L184-L196

should have [DoesNotReturnIf(false)] on condition.

[rainersigwald]

This will require targeting .NET Core 3/.NET Standard 2.1+.

[rainersigwald]

I started on this a long time ago and this was my WIP: rainersigwald@119ab18. It was long enough ago that I don't remember anything I did but it might be useful to look at https://github.com/rainersigwald/msbuild/pull/new/nullable-ErrorUtilities

[huulinhnguyen-dev]

This issue has been completed. All requested nullable reference type annotations have been added to ErrorUtilities.cs:

• [DoesNotReturn] on ThrowInternalError and similar methods
• [NotNull] on VerifyThrowInternalNull parameter
• [DoesNotReturnIf(false)] on VerifyThrow condition parameters

The file now has comprehensive nullable annotations throughout, providing excellent compile-time null safety analysis.

[KalleOlaviNiemitalo]

#10272 for reference.