GDA-5571 Refactor code for getting the calling class in GDALogger

The old calls called Reflection.getCallerClass with 2, but the new method must
call it with 3, since the newly-introduced method adds an extra stack frame.
GDA-5571 Fix GDALogger to cope with broken getCallerClass method in 7u25
GDA-5571 Add comment to GDALogger pointing out that getCallerClass is deprecated
Merge branch 'GDA-5571' into 8.34