fix(datastore): Add missing onError handlers

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:
#2817

Description of changes:

• Added RxLint lint checks. These checks highlight potential RxJava errors such as missing error handlers.
• Resolved all RxLint errors

How did you test these changes?

• Manual testing

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[mattcreaser]

This PR is failing on some integration tests. I will try to investigate when I get time.