[clang-format] Treat NTTP default values as expressions

clang-format already has logic to threat the right-hand side of an
equals sign. This patch applies that logic to template defaults,
which are likely to be non-template type parameters in which case the
default value should be annotated as an expression.
This should mostly only ever apply to bool and &&.

Fixes https://github.com/llvm/llvm-project/issues/61664

Reviewed By: MyDeveloperDay, owenpan

Differential Revision: https://reviews.llvm.org/D146760