[clang] [analyzer] Avoid creating LazyCompoundVal when possible (PR #116840)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat approved this pull request.

The change LGTM and I'm happy to hear that you're improving the handling of compound values. I hope that these foundational improvements will help further development of checkers that deal with structured data. (Perhaps even the iterator checkers could be stabilized eventually...)

On our downstream branch this commit breaks a few tests, but I think that this just exposes faults of our internal-use checkers (which we'll update eventually).

By the way I think there is a typo in the PR description: the word "not" is missing from the location where I marked it in brackets:
>  I should [not] have just blindly create  an LCV by calling createLazyBinding(), but rather check if I can apply the shortcut
(Also, "create" should be "created".)

https://github.com/llvm/llvm-project/pull/116840