Assembly-wide UseStaticMapper

Description

This PR makes the UseStaticMapper attribute usable at the assembly level, so the specified mappers are available for all other mappers without needing to be specified explicitly.

Remarks

• I thought this would be a useful feature while working with Mapperly, then I saw there is already an open issue for this, so I implemented it. 🙂
• Instead of ImmutableArray<UseStaticMapperConfiguration> _globalStaticMappers; I considered passing it to the Build method. Does that make more sense? But if yes, then some other input also, which is not a dependency but a parameter.
• AttributeDataAccessor.Access<UseStaticMapperAttribute<object>, UseStaticMapperConfiguration>(attributeData); also processes the non-generic variant, so I left it this way.
• A little bit restructured the methods in ExternalMappingsExtractor to better fit this new feature.
• The integration test on the generic variant was removed in the end. This way, no conditional compilations are needed.

Fixes #1146

Checklist

• The existing code style is followed
• The commit message follows our guidelines
• Performed a self-review of my code
• Hard-to-understand areas of my code are commented
• The documentation is updated (as applicable)
• Unit tests are added/updated
• Integration tests are added/updated (as applicable, especially if feature/bug depends on roslyn or framework version in use)