Cannot create packages for Google PlayStore

Thanks to the change 9efaf8bae914958a09d29a4cdbf62e345f3e6369 which fixes QTBUG-103281, there is no way to specify the --release flag for normal cmake based builds anymore.

This results in debug packages being created by androiddeployqt which are not accepted by the Google PlayStore.

There was a comment added to QTBUG-103281 back in December about this already, but maybe this was just ignored, because THAT bug was closed?

I see 2 possible options here:
1) extend qt6_android_add_apk_target to add something like QT_ANDROIDDEPLOYQT_EXTRA_ARGS to its extra_args variable
2) at least detect the current build type and automatically add the missing --release flag to the androiddeployqt command line, if it's a release build

Ideally we should do both: (1) for future flexibility and (2) to unbreak all existing cmake based user code.