[mlir][Conversion] Rename the MemRefToLLVM pass

Since the recent MemRef refactoring that centralizes the lowering of
complex MemRef operations outside of the conversion framework, the
MemRefToLLVM pass doesn't directly convert these complex operations.

Instead, to fully convert the whole MemRef dialect space, MemRefToLLVM
needs to run after `expand-strided-metadata`.

Make this more obvious by changing the name of the pass and the option
associated with it from `convert-memref-to-llvm` to
`finalize-memref-to-llvm`.
The word "finalize" conveys that this pass needs to run after something
else and that something else is documented in its tablegen description.

This is a follow-up patch related to the conversation at:
https://discourse.llvm.org/t/psa-you-need-to-run-expand-strided-metadata-before-memref-to-llvm-now/66956/14

Differential Revision: https://reviews.llvm.org/D142463