[clang] [clang][ASTMatcher] Handle variable templates in `isInstantiated` and `isInTemplateInstantiation` matchers (PR #110666)

[Fred Tingaud via cfe-commits]

frederic-tingaud-sonarsource wrote:

Thanks @AaronBallman!
Yes, if you could land the changes, that would be great.

https://github.com/llvm/llvm-project/pull/110666