Upgrade build dependencies for the project

- Upgrade to Gradle 8.11
- Upgrade to Android Gradle Plugin 8.7.2
- Remove deprecated android.defaults.buildfeatures.buildconfig=true
  gradle property, it is not needed as mastodon/build.gradle already
  sets android { buildFeatures { buildConfig true } }
- Move plugin repository definition to settings.gradle to match latest
  Gradle practices
- Move to using plugin {} mechanism to add Android Gradle Plugin to
  match the latest Gradle practices
- Remove root project clean task as this project does not produce any
  real artifacts, it seems to be leftover from original Android new
  project template

gradle.properties

@@ -17,7 +17,6 @@ org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
 android.useAndroidX=true
 # Automatically convert third-party libraries to use AndroidX
 android.enableJetifier=false
-android.defaults.buildfeatures.buildconfig=true
 android.nonTransitiveRClass=true
 android.nonFinalResIds=false
-org.gradle.configuration-cache=true
+org.gradle.configuration-cache=true