ohos: position: move enums to QtOhosPositioning::enums

The qtbase generator now requires a Qt module name and derives the
namespace root and the header file name from it, so the plugin's header
can no longer be regenerated in its current form. The header is internal
to the plugin and cannot collide with any other, but one rule for every
generated header is simpler than distinguishing plugins from modules.

Regenerate it with --qt-module Positioning: it becomes
qohospositioningenums.h and defines the enums in
QtOhosPositioning::enums instead of QtOhos::enums.

Adapt the plugin's includes and using declarations accordingly.

Task-number: QTBUG-149934
Pick-to: 6.12
Change-Id: Ie72b98896a02234ff96aeb0e094073f47147d7b7
Reviewed-by: Dawid Śliwa <dawid.sliwa@qt.io>
Reviewed-by: Liang Qi <liang.qi@qt.io>