Fix trim annotations on generated validation code

[sbomer]

The generated code currently produces a trim warning at k.ContainingType.GetProperty:

ValidatableInfoResolver.g.cs(263,32): error IL2075: 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicProperties' in call to 'System.Type.GetProperty(String)'. The return value of method 'Microsoft.AspNetCore.Http.Validation.Generated.ValidationAttributeCache.CacheKey.ContainingType.get' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.

[BrennanConroy]

Seems like we should have a linker/aot verification test.
e.g. https://github.com/dotnet/aspnetcore/blob/main/src/SignalR/server/SignalR/test/Microsoft.AspNetCore.SignalR.Tests/NativeAotTests.cs

[dotnet-policy-service]

Looks like this PR hasn't been active for some time and the codebase could have been changed in the meantime.
To make sure no conflicting changes have occurred, please rerun validation before merging. You can do this by leaving an /azp run comment here (requires commit rights), or by simply closing and reopening.