feat: Process required keyword like MemberRequiredAttribute

[Eideren]

PR Details

Now that required is an actual keyword, we can use it to notify users when some of their components have missing references, just like our MemberRequiredAttribute.

required is an essential part of projects using the nullable reference feature, using it in stride to benefit from null-state analysis from both the compiler and our asset builder requires writing a fairly redundant property definition:

[MemberRequired] public required MyRef myRef { get; set; }

When the intent of the attribute is already made clear through the use of the required keyword.

public required MyRef myRef { get; set; }

Related Issue

None

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My change requires a change to the documentation.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have built and run the editor to try this change out.

Hopefully you have some time to get back to me about this one @manio143 , would like to hear your thoughts given that this is your feature.

[manio143]

Looks good. Small suggestion would be to add a unit test for that case (as there already is one for the attributes) here https://github.com/stride3d/stride/blob/c2497b57eaba3ce84ea77a3ca14e5aeafafd3c88/sources/engine/Stride.Assets.Tests/TestMemberRequiredComponentChecks.cs

[Eideren]

There we go, covered both the keyword and the keyword with the attribute set to error. Can you check again @manio143 ?