Revert 741978d7 and things that landed on top of it.

741978d7 made clang produce output that's 2x as large at least in
sanitizer builds. https://reviews.llvm.org/D83892#2470185 has a
standalone repro.

This reverts the following commits:

Revert "[clang][cli] Port CodeGenOpts simple string flags to new option parsing system"
This reverts commit 95d3cc67.

Revert "[clang][cli] Port LangOpts simple string based options to new option parsing system"
This reverts commit aec2991d.

Revert "[clang][cli] Streamline MarshallingInfoFlag description"
This reverts commit 27b7d646.

Revert "[clang][cli] Port LangOpts option flags to new option parsing system"
This reverts commit 383778e2.

Revert "[clang][cli] Port CodeGen option flags to new option parsing system"
This reverts commit 741978d7.