improve: use Base64 implementation from jre

[bokken]

Removes Base64 from org.postgresql.util and updates use in RecoveredXid with jre Base64.

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:

• [y] Does this break existing behaviour? If so please explain.
  It removes the Base64 utility class
• 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?

[davecramer]

hopefully nobody uses the Util class. We could always deprecate that and then remove it later. I'm ambivalent as it's a private API

[vlsi]

@bokken , I believe this removed a class without aging it in @Deprecated state for a while.

Please refrain from removing classes as people might still be using them: https://github.com/search?l=Scala&q=org.postgresql.util.base64&type=Code

[jorsol]

While I generally agree that backward compatibility is extremely important in this project, I'm ambivalent to resurrecting this class just to mark it as @Deprecated, it's an internal API after all (even if it's not marked as such).

I'm not against of resurrecting that class either just to mark it as @Deprecate but there is no benefit for it, in GitHub search, you will find all kinds of usage, many toy projects, and also unmaintained code that doesn't reflect a real usage, there might be valid real-world production projects, but those should not use this class anyway.

[sehrope]

+1 to not adding it back. The util classes are not part of the public API.

Anybody that was using it would see a compile time error. No runtime behavior of anything public has changed.

If we haven't done so already, we should also explicitly declare in the README or the docs the packages that we consider "official" API.

[davecramer]

I see no harm in adding it back @deprecated ...
+1 to documenting what we consider the official API.