[clang] [clang] Update argument checking tablegen code to use a 'full' name (PR #99993)

[Nikita Popov via cfe-commits]

nikic wrote:

This causes significant compile-time regressions, especially for unoptimized builds: https://llvm-compile-time-tracker.com/compare.php?from=39b6900852e7a1187bd742ba5c1387ca1be58e2c&to=2acf77f987331c05520c5bfd849326909ffce983&stat=instructions:u

You probably need to separately match the syntax and the name without constructing a temporary `std::string`.

https://github.com/llvm/llvm-project/pull/99993