[clang] [llvm] [DebugInfo] Introduce metadata flag for -gsimple-template-names and optimize template params in skeleton CU. (PR #174904)

[Liu Ke via cfe-commits]

Sockke wrote:

> Right now this flag is on Subprogram level, should it be on CU level?

`-gsimple-template-names` only simplifies names for template functions that meet the conditions, not all in CU, so this flag should be on  Subprogram level.

https://github.com/llvm/llvm-project/pull/174904