Bump to Mokito 4

[Abacn]

Part of #34056 . Powermock is not compatible with Mockito 4, had to remove its usage in most tests, if applicable

• Split tests need mockStatic outside of DataflowTest
  To be able to run DataflowTest internally which did not support mockStatic

• Remove usage of powermock for GcpIO, KafkaIO, DataflowRunner tests

• Minimize powermock dependency for Flink runner

Please add a meaningful description for your change here

---

Thank you for your contribution! Follow this checklist to help us incorporate your contribution quickly and easily:

• Mention the appropriate issue in your description (for example: addresses #123), if applicable. This will automatically add a link to the pull request in the issue. If you would like the issue to automatically close on merging the pull request, comment fixes #<ISSUE NUMBER> instead.
• Update CHANGES.md with noteworthy changes.
• If this contribution is large, please file an Apache Individual Contributor License Agreement.

See the Contributor Guide for more tips on how to make review process smoother.

To check the build health, please visit https://github.com/apache/beam/blob/master/.test-infra/BUILD_STATUS.md

GitHub Actions Tests Status (on master branch)

See CI.md for more information about GitHub Actions CI or the workflows README to see a list of phrases to trigger workflows.

[github-actions]

Checks are failing. Will not request review until checks are succeeding. If you'd like to override that behavior, comment assign set of reviewers

[Abacn]

assign set of reviewers

[github-actions]

Assigning reviewers. If you would like to opt out of this review, comment assign to next reviewer:

R: @m-trieu for label java.
R: @damccorm for label build.
R: @damondouglas for label io.
R: @fozzie15 for label kafka.

Available commands:

• stop reviewer notifications - opt out of the automated review tooling
• remind me after tests pass - tag the comment author after tests pass
• waiting on author - shift the attention set back to the author (any comment or push by the author will return the attention set to the reviewers)

The PR bot will only process comments in the main thread (not review comments).

[Abacn]

PreCommit Flink Container passed, failed at tearDown dataproc, infra flakiness

[Abacn]

testOnNewWorkerMetadata_redistributesBudget failed twice due to #28957. Test succeeded locally. not related to this change

[damccorm]

Thanks!