[clang] [clang-tools-extra] [clang][modules] Serialize `CodeGenOptions` (PR #146422)

[Jan Svoboda via cfe-commits]

jansvoboda11 wrote:

I put up https://github.com/llvm/llvm-project/pull/146766 and https://github.com/llvm/llvm-project/pull/146910. Will rebase this PR on top of those once those get approved & merged.

https://github.com/llvm/llvm-project/pull/146422