Goal is to make option setup more similar to the other "simple" pages.
The GdbOptionPage is now separated in the setup code, but aggregated
into the old place and accessed there.
The per-backend separation seem quite weak, a full split would currently
need to have include gdb/* in several places now is an indication
that the gdb/non-gdb split in the options is dubious at best.
Change-Id: Iad210016739aa4a63645731e16825f546bdd5e8a
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
