improv: Use jre utf-8 decoding

[bokken]

Remove use of custom utf-8 decoding as the jre implementation is nearly always faster in jdk 11+. Additionally, improvements continue to be made in the jdk.

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

New Feature Submissions:

1. Does your submission pass tests?
2. Does ./gradlew autostyleCheck checkstyleAll pass ?
3. Have you added your new test classes to an existing test suite in alphabetical order?

Changes to Existing Features:

• Does this break existing behaviour? If so please explain. Invalid utf-8 will no longer result in failure, but rather use of unicode replacement char.
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully run tests with your changes locally?