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

[Danila Malyutin via cfe-commits]

danilaml wrote:

Is it even possible for `isSafeToSpeculativelyExecute` to return `true` now with the default (nullptr) CtxI? 

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