Handle transitive buildscript dependencies that were only present in JCenter

[clayburn]

This change fixes the broken Samza build by rewriting some buildscript dependencies that were only present in JCenter, which is now shutdown. In particular, com.burgstaller:okhttp-digest:1.10 and org.ysb33r.gradle:grolifant:0.12, transitive dependencies of com.github.jruby-gradle:jruby-gradle-plugin:2.0.2, only existed in JCenter.

The change:

• Rewrites the group of okhttp-digest from com.burgstaller to io.github.rburgst
• Updates okhttp-digest from 1.10 to 1.21
• Updates grolifant from 0.12 to 0.12.1

Ideally, jruby-gradle-plugin, which transitively depends on these plugins would be updated to resolve these issue, but this change fixes the problems in the meantime. The plugin has not been updated or released in quite some time. This PR has not well-tested to see how compatible these new versions are with the Samza build.

For more information, see:

• Impact of final JCenter shutdown on Gradle Plugin Portal | Gradle Blog
• JRuby Gradle plugin does not resolve anymore jruby-gradle/jruby-gradle-plugin#451
• Version 1.10 of published artifact is gone rburgst/okhttp-digest#86