[clang] Refactor clang's keyword enable/disable mechanism to allow lldb to re-use it (#165323)
lldb's CPlusPlusNameParser is currently identifying keywords using it's
own map implemented using clang/Basic/TokenKinds.def. However, it does
not respect the language options so identifiers can incorrectly
determined to be keywords when using languages in which they are not
keywords.
Rather than implement the logic to enable/disable keywords in both
projects it makes sense for lldb to use clang's implementation.
See #164284 for more information