[clang] [analyzer] Don't assume third iteration in loops (PR #119388)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

The logic that I added only affects the handling of the condition part of loop statements, so it has absolutely no effect on the handling of code that implements similar looping behavior with different language features. I added a testcase to document this (and as an example, show the behavior of `while (1) if (cond) break;` which is IMO the least different way of looping).

https://github.com/llvm/llvm-project/pull/119388