Change https://reviews.llvm.org/D140059 exposed the following crash in
Z3Solver, where bit widths were not checked consistently with that
change. This change makes the check consistent, and fixes the crash.

```
clang: <root>/llvm/include/llvm/ADT/APSInt.h:99:
  int64_t llvm::APSInt::getExtValue() const: Assertion
  `isRepresentableByInt64() && "Too many bits for int64_t"' failed.
...
Stack dump:
0. Program arguments: clang -cc1 -internal-isystem <root>/lib/clang/16/include
  -nostdsysteminc -analyze -analyzer-checker=core,unix.Malloc,debug.ExprInspection
  -analyzer-config crosscheck-with-z3=true -verify reproducer.c

 #0 0x00000000045b3476 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
  <root>/llvm/lib/Support/Unix/Signals.inc:567:22
 #1 0x00000000045b3862 PrintStackTraceSignalHandler(void*)
  <root>/llvm/lib/Support/Unix/Signals.inc:641:1
 #2 0x00000000045b14a5 llvm::sys::RunSignalHandlers()
  <root>/llvm/lib/Support/Signals.cpp:104:20
 #3 0x00000000045b2eb4 SignalHandler(int)
  <root>/llvm/lib/Support/Unix/Signals.inc:412:1
 ...
 #9 0x0000000004be2eb3 llvm::APSInt::getExtValue() const
  <root>/llvm/include/llvm/ADT/APSInt.h:99:5
  <root>/llvm/lib/Support/Z3Solver.cpp:740:53
  clang::ASTContext&, clang::ento::SymExpr const*, llvm::APSInt const&, llvm::APSInt const&, bool)
  <root>/clang/include/clang/StaticAnalyzer/Core/PathSensitive/SMTConv.h:552:61
```

Reviewed By: steakhal

Differential Revision: https://reviews.llvm.org/D142627

(cherry picked from commit f027dd55f32a3c1803fc3cbd53029acee849465c)