[clang] [llvm] [Loads] Check context instruction for context-sensitive derefability (PR #109277)

[Danila Malyutin via cfe-commits]

danilaml wrote:

@nikic ah, yeah. I remember the issue with dereferenceable w.r.t. free discussion. Guess will have to roll something for allocations that don't have this problem.

https://github.com/llvm/llvm-project/pull/109277