[clang] [analyzer] Handle [[assume(cond)]] as __builtin_assume(cond) (PR #116462)

[Balazs Benics via cfe-commits]

https://github.com/steakhal commented:

> As far as I know, to eliminate the warning emitted corresponding to the FIXME comment, we need to implement a new Checker for attributes; we can do this in a second PR to avoid scope creep for this issue/PR.

Agreed. I had a look at the exploded graph and look correct to me.

I think I'll come back to this PR, apply some really minor recommendations and I think we can land it.
Thank you so much for pushing for this so hard. I really appreciate it.

Expect me back on this in a couple of days.

https://github.com/llvm/llvm-project/pull/116462