[clang] [clang] improve diagnostics for enums (PR #204682)

[Matthias Wippich via cfe-commits]

Tsche wrote:

I've added a printing policy option to opt out of this pretty printing for `-ast-print`. We should probably rename the very similar option `UseEnumerators` to something along the lines of `PrettyEnumsInTemplateArguments`. I'll send a separate patch for that.

https://github.com/llvm/llvm-project/pull/204682