[clang-tidy] Ignore other members in a union if any member of it is...

[clang-tidy] Ignore other members in a union if any member of it is initialized in cppcoreguidelines-pro-type-member-init

If a union member is initialized, the other members of the union are still suggested to be initialized in this check.  This patch fixes this behavior.
Reference issue: https://github.com/llvm/llvm-project/issues/54748

Reviewed By: njames93

Differential Revision: https://reviews.llvm.org/D127293