[MLIR][ControlFlowToLLVM] Remove typed pointer support (#70733)

This commit removes the support for lowering ControlFlow to LLVM dialect
with typed pointers. Typed pointers have been deprecated for a while now
and it's planned to soon remove them from the LLVM dialect.

Related PSA:
https://discourse.llvm.org/t/psa-removal-of-typed-pointers-from-the-llvm-dialect/74502