Changes

contrib/android: bump compile/targetSdkVersion to 31

Required by Google Play for newer Android versions.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>

contrib/android: update build parameters for Android 12

Main activity with intent-filter required "android:exported" parameter,
and it must be "true" because this activity may be called by other apps
or the launcher.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>

contrib/android: bump android app subversion to 1.5.2

We updated some build parameters in previous commits.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>