Android: add Gradle composite build to manage JAR projects

With a Gradle-enabled Qt build, it's easy now to manage all
Qt modules' JAR builds in one place from an IDE, and that's
what's being done here with Gradle composite builds. This
adds each module's JAR in the qt super repo and each module
also defines its potential dependencies (e.g. Qt6Android.jar).

This also update .gitignore with Gradle, JDTLS and IntelliJ
ignores, and moves the existing .gitignore from the provision
android_gradle project to the root.

Task-number: QTBUG-132915
Change-Id: I4573768c394a4c25347eeb8ce6e2ddf7e57796ef
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

.gitignore

@@ -11,3 +11,16 @@ build-*/
 init-repository.opt
 init-repository.opt.in
 config.tl.opt
+
+# CLion generated files
+.idea
+
+# Gradle generated files
+.gradle/
+local.properties
+
+# JDTLS generated files
+.project
+.classpath
+.settings/
+bin/