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/wrapper/gradle-wrapper.properties

@@ -1,7 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionSha256Sum=e111cb9948407e26351227dabce49822fb88c37ee72f1d1582a69c68af2e702f
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.1.1-bin.zip
+distributionSha256Sum=57dafb5c2622c6cc08b993c85b7c06956a2f53536432a30ead46166dbca0f1e9
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11-bin.zip
 networkTimeout=10000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists