[llvm] [GlobalISel] Add GIM_CheckMachineOperandType for matching metadata operands (PR #191389)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

Should get tablegen test?

This looks like it's doing 2 different things. Verifying the type of the operand isn't related to verifying an operand is metadata? I don't understand why we would need a new type matching mechanism. That's fundamental to all of the existing matching? 

https://github.com/llvm/llvm-project/pull/191389