[clang][cli] Use variadic macros for parsing/generating

This patch makes all macros forwarding to `PARSE_OPTION_WITH_MARSHALLING` and `GENERATE_OPTION_WITH_MARSHALLING` variadic.

Sice we will be splitting up all CompilerInvocation parts, this will allow us to avoid a lot of boilerplate code.

The local macros prefix forwarded arguments with local variables required by the main macros. The `{THIS,NO}_PREFIX` macros make it possible for forwarding macros in member functions (`parseSimpleArgs`, `generateCC1CommandLine`) to prefix keypaths with `this->`. (Some build bots seem to require that.)

Reviewed By: dexonsmith

Differential Revision: https://reviews.llvm.org/D95532