[mlir][MemRef] Introduce a memref.extract_metadata op.

This is the counterpart of `memref.reinterpret_cast` and is useful to lift
strided memref manipulation out of the LLVM dialect.

Discussion: https://discourse.llvm.org/t/extracting-dynamic-offsets-strides-from-memref/64170

Differential Revision: https://reviews.llvm.org/D132243