[mlir][llvm] Switch remaining LLVM dialect tests to opaque pointers.

The revision switches the remaining LLVM dialect tests to use opaque
pointers. Selected tests are copied to a postfixed test file for the
time being.

A number of tests disappear once we fully switch to opaque pointers.
In particular, all tests that check verify a pointer element type
matches another type as well as tests of recursive types.

Part of https://discourse.llvm.org/t/rfc-switching-the-llvm-dialect-and-dialect-lowerings-to-opaque-pointers/68179

Reviewed By: Dinistro, zero9178

Differential Revision: https://reviews.llvm.org/D146726