Bump Android SDK to 28, Build Tools to 28.0.2, Gradle to 4.7, Gradle Plugin to 3.2.0 (#21632)

Summary:
This PR is bumping compileSdkVersion to 28, buildToolsVersion to 28.0.2, Gradle to 4.7, Android Gradle plugin to 3.2.0.

Gradle 4.7 added support for Java 10 and 11.

allow-large-files

Release Notes:
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[ANDROID] [ENHANCEMENT] [SDK] - bump to 28

Pull Request resolved: https://github.com/facebook/react-native/pull/21632

Reviewed By: mdvacca

Differential Revision: D13084836

Pulled By: hramos

fbshipit-source-id: e0f493881e80e87faf8c3ef1ac77044495966a49