CoreCLR Interpreter - Shared generics support

[davidwrighton]

Basic shared generics support will be in once PR #116357 is merged, but there remain a number of additional issues

• Support for box with a generic type which varies by type parameter
• Support for unbox.any with a generic type which varies by type parameter
• Support for isinst with a generic type which varies by type parameter
• Support for castclass with a generic type which varies by type parameter
• Support for static fields on a type which varies by type parameter
• Support for callvirt fallback to ldvirtftn behavior, will probably require adding support for the ldvirtftn opcode + calli opcode
• Support for constrained calls to classes
• Support for constrained calls to static virtual methods defined on classes. will probably require adding support for the calli opcode
• Support for IL stub implementations of unboxing/unboxing and instantiating helpers
• Support for constrained dispatch to structs from generic code, particularly with shared generics involved. Will involve respecting the CORINFO_THIS_TRANSFORM returned from getCallInfo
• Handling of catch of a generic where which generic is dependent on the context argument to the method

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[EgorBo]

Does the Catch clause (EH) with Exception requiring runtime lookup need to be in the list too? (catch (MyException<T> exc))

[davidwrighton]

@EgorBo yes, we need to handle that, I'm surprised it hasn't come up in testing, but ... we'll get to it.