[clang-tidy] Add scoped enum constants to identifier naming check

Added option `ScopedEnumConstant(Prefix|Case|Suffix)` to readability-identitied-naming.
This controls the style for constants in scoped enums, declared as enum (class|struct).
If this option is unspecified the EnumConstant style will be used instead.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D89407