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

[Balazs Benics via cfe-commits]

steakhal wrote:

I held this patch off because during testing I saw some interesting-looking (seemingly) FPs.
I wanted to have a look, but I couldn't find disputable evidence for proving that they were FPs.
I still believe that this patch is solid, and even if it exposes some FPs, those are more likely to be caused by some other bug. We may need to come back to this, or any other patch related to LCVs and copying structs prior the next release.
Keep in mind this.

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