runtime: use EnumTimeFormatsEx instead of EnumWindows in callback tests

Use EnumTimeFormatsEx() to test panics across callback boundaries
instead of EnumWindows(). EnumWindows() is incompatible with Go's panic
unwinding mechanism. See the associated issue for more information.

Updates #26148

Change-Id: If1dd70885d9c418b980b6827942cb1fd16c73803
Reviewed-on: https://go-review.googlesource.com/c/155923


Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>