[clang] [clang-tools-extra] Handle recording inheritance for templates (PR #177273)

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timon-ul wrote:

>  I guess it boils down to: do we want to report inheritance even if there is no instantiation for this inheritance?

After sleeping a night over this I am more in favour of keeping this behaviour. Simply put, a user that wrote some template inheritance might want to find this case even without instantiations, after all it is in the code.

https://github.com/llvm/llvm-project/pull/177273