Support modern Android project structures

The current Qt for Android project consists of a folder containing the app and its dependencies. At this point, it's considered more of a legacy of dealing with Android projects.

Under this, the aim is to support more modern project structure detailed in https://developer.android.com/build. This would allow us to have:

• A more modern and universal structure that can work for Qt and for native Android
• Supporting feature delivery QTBUG-116683
• Manage multiple dependencies and subprojects https://docs.gradle.org/current/userguide/multi_project_builds.html
• Support flavors, multiple APKs, and manifests (e.g. QTBUG-77172)

Under this, we can also expect less or no usage for the legacy Qt for Android bridges (the JSON settings file) and directly use Gradle properties files (settings.properties, local.properties, gradle.properties).