Contributes to #65112

• [mono] Support AcceptByRefLike metadata generic param attribute #94421
• JIT+AOT boxing elision support
  • generic sharing support: As a first cut we should probably just always create specific instance code for byreflike instances. On the other hand, the gpAcceptByRefLike param may allow gsharedvt to do a better job (since we know we would never need to box values of the type). Done in [mono] Add basic ref struct support for generic parameter #99081
• Interp boxing elision support
  • [mono] box related IL instruction sequence optimization for interpreter #99379
• Need to delay type loading error until runtime for array of T with ByRefLike type #99165

The runtime design is specced out here: https://github.com/dotnet/runtime/blob/main/docs/design/features/byreflike-generics.md

There are tests in https://github.com/dotnet/runtime/tree/main/src/tests/Loader/classloader/generics/ByRefLike