[clang][cli] Parse Lang and CodeGen options separately

[clang][cli] Parse Lang and CodeGen options separately

This patch moves the parsing of `{Lang,CodeGen}Options` from `parseSimpleArgs` to the original `Parse{Lang,CodeGen}Args` functions.

This ensures all marshalled `LangOptions` are being parsed **after** the call `setLangDefaults`, which in turn enables us to marshall `LangOptions` that somehow depend on the defaults. (In a future patch.)

Now, `CodeGenOptions` need to be parsed **after** `LangOptions`, because `-cl-mad-enable` (a `CodeGenOpt`) depends on the value of `-cl-fast-relaxed-math` and `-cl-unsafe-math-optimizations` (`LangOpts`).

Unfortunately, this removes the nice property that marshalled options get parsed in the exact order they appear in the `.td` file. Now we cannot be sure that a TableGen record referenced in `ImpliedByAnyOf` has already been parsed. This might cause an ordering issues (i.e. reading value of uninitialized variable). I plan to mitigate this by moving each `XxxOpt` group from `parseSimpleArgs` back to their original parsing function. With this setup, if an option from group `A` references option from group `B` in TableGen, the compiler will require us to make the `CompilerInvocation` member for `B` visible in the parsing function for `A`. That's where we notice that `B` didn't get parsed yet.

Reviewed By: Bigcheese

Differential Revision: https://reviews.llvm.org/D94682