[llvm][ADT] Move TypeSwitch class from MLIR to LLVM

[llvm][ADT] Move TypeSwitch class from MLIR to LLVM

This class implements a switch-like dispatch statement for a value of 'T' using dyn_cast functionality. Each `Case<T>` takes a callable to be invoked if the root value isa<T>, the callable is invoked with the result of dyn_cast<T>() as a parameter.

Differential Revision: https://reviews.llvm.org/D78070