Support filter for exception handling

[antoyo]

rust-lang/rust#104070 (comment)

For this C++:

void b() noexcept {
    f();
}

we get this gimple:

void b ()
{
  try
    {
      f ();
    }
  catch
    {
      <<<eh_must_not_throw (terminate)>>>
    }
}

Seems like we just need to set TRY_CATCH_IS_CLEANUP on TRY_CATCH_EXPR.

EH_FILTER_EXPR might be better.

The test tests/run-make/forced-unwind-terminate-pof tests this.