Fix handling of NullReferenceException in VSD on ARM (#25627)

Fix handling of NullReferenceException in VSD on ARM (#25627)

* Fix handling of NullReferenceException in VSD on ARM

There was a problem with handling NullReferenceExceptionHandling stemming
from virtual dispatch stub on ARM Linux. While the primary exception was
handled correctly, if the exception was rethrown or another exception
was thrown from the catch handler, it was reported as unhandled even
though there was a proper handler.
The issue was caused by exception unwinding that was unable to unwind past
the frame of the virtual dispatch stub in this case. Such stub is generated
at runtime and there is no unwind info for it.

The fix is to explicitly check for the stub frame and skip it during first
and second pass of exception handling.