[clang] [analyzer] Fix null-pointer dereference in PthreadLockChecker (PR #210912)

[Arseniy Zaostrovnykh via cfe-commits]

necto wrote:

> I'll try to use `simplifyToSVal` in the 3 places `simplify` is used in and handle concrete values there

I removed the `simplify` wrapper and inlined it in the 3 places where it was used. You can see the effect in the commit history:

- 934cd3ccc7fd Revert "Fix PthreadLockChecker" - remove the sympomatic fix
- 1ae1e1dc5b8d Add a test case demonstrating missed simplification
   demonstrate the imprecision introduced by `simplify`. Note that the imprecision is masked in the third case (`assumeSymUnsupported`), but it still leads to some wasted work.
- dcb89e17978a Fix the simplification blind spot for concrete integers
  Implement a proper minimal fix. It also made the z3-refutation test moot because it relied on this imprecision
  to demonstrate the difference z3 brings. It is a further proof that this fix reduces number of infeasible paths we explore.
- 96bdb09b678a Restore meaningful z3-crosscheck.c test
  Z3 is still useful, so I let Claude find another approximation point of the range constraint manager compared to Z3.

It is likely there is more simplification that could be done, but I wanted to keep the fix scope narrow to avoid regression risks.

How does it look, @steakhal ?

https://github.com/llvm/llvm-project/pull/210912