[Driver] Clean up some Separate form options

Drop the `Separate` form of `-fmodule-name X`, `-fprofile-remapping-file X`, and `-frewrite-map-file X`.
To the best of my knowledge they are not used. Their conventional Joined forms (`-fFOO=`) should be used instead.

`-fdebug-compilation-dir X` is used in several places, e.g.  chromium/infra/goma.
It is also advertised in http://blog.llvm.org/2019/11/deterministic-builds-with-clang-and-lld.html
So we keep it but make the EQ form canonical and the Separate form an alias.

Differential Revision: https://reviews.llvm.org/D96886