[TIMOB-28455] Android: Update gradle build tools to 4.2.x

*Summary:* Titanium currently builds with "com.android.tools.build:gradle" tool version 4.1.2. We should update it to 4.2.1. https://developer.android.com/studio/releases/gradle-plugin#4-2-0 *To-Do:* We must update the following files... https://github.com/appcelerator/titanium_mobile/blob/master/android/build.gradle https://github.com/appcelerator/titanium_mobile/blob/master/android/templates/build/root.build.gradle In folder titanium_mobile/android, we must execute below command line to upgrade gradle wrapper library to version [6.9](https://docs.gradle.org/6.9/release-notes.html).

./gradlew wrapper --distribution-type all --gradle-version 6.9

*Note:* You must use Android Studio 4.2.x to build the Titanium SDK after this change.