[LAA] Drop alias scope metadata that is not valid across iterations (#79161)

LAA currently adds memory locations with their original AATags to AST.
However, scoped alias AATags may be valid only within one loop
iteration, while LAA reasons across iterations.

Fix this by determining which alias scopes are defined inside the loop,
and drop AATags that reference these scopes.

Fixes https://github.com/llvm/llvm-project/issues/79137.