[clang] Pass LangOpts from CompilerInstance to DependencyScanningWorker (PR #93753)

[Nishith Kumar M Shah via cfe-commits]

nishithshah2211 wrote:

@cor3ntin @Sirraide I put up a draft PR to get some feedback and see if the changes here make sense or not.

Also tagging @pogo59 since I received good feedback/pointers here: https://discourse.llvm.org/t/looking-for-help-with-accessing-langopts-from-the-actual-compiler-invocation/79228.

My main concern is mostly around introducing `LangOpts` within `ensureDirectiveTokensArePopulated` API.

I'll add new tests and fix existing tests in the next commit on this PR if the source changes seem reasonable.

https://github.com/llvm/llvm-project/pull/93753