Allow JRE configuration by extensions..

[BarDweller]

Summary

Moves the post-extraction configuration of the JRE to a public method (that can be used by extensions that install a JRE through other means)..

Use Cases

Checklist

• [x] I have viewed, signed, and submitted the Contributor License Agreement.
• [x] I have linked issue(s) that this PR should close using keywords or the Github UI (See docs)
• [x] I have added an integration test, if necessary.
• [x] I have reviewed the styleguide for guidance on my code quality.
• [x] I'm happy with the commit history on this PR (I have rebased/squashed as needed).