Draft: add gradle dependency verification

[David-Development]

Adding checksums to Android repos like android-common for gradle based build toolchain, see https://docs.gradle.org/current/userguide/dependency_verification.html.

Reference: nextcloud/android-common#252

TODO: We'll have to move to renovatebot which is capable of update checksums when updating dependencies, see https://docs.renovatebot.com/modules/manager/gradle/ -> nextcloud/Android-SingleSignOn#640

[AndyScherzinger]

Also useful to add

org.gradle.dependency.verification.console=verbose

to

gradle.properties

to make gradle a bit more chatty when it comes to verification output when failing