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

AaronBallman merged 3 commits intollvm:mainllvm/llvm-project:mainfrom

frederic-tingaud-sonarsource:ft/var-templatefrederic-tingaud-sonarsource/llvm-project:ft/var-templateCopy head branch name to clipboard