produce a signed APK for release

[siddarthkay]

Description

• An signed APK with a password protected keystore and a private key is required for releasing to the google playstore.

[siddarthkay]

androiddeployqt accepts --sign which is very convenient to get this done
https://doc.qt.io/qt-6/android-deploy-qt-tool.html#command-line-arguments

[siddarthkay]

• mobile: build a signed android app #18992 illustrates PR workflow for producing signed android APK

• Release test aab #19017 illustrates PR workflow during release

CI will produce AAB when targeting release branch and APK when targeting master.
We can use the AAB to publish release in google play store and APK can be used to add to github release page.