Update our checkstyle version.

We should update our checkstyle version. We tried that before but didn't update the version in the workflow. We also did not fix issues that the new versions are checking for.

Currently, running ./gradlew checkstyleMain and ./gradlew checkstyleTest passes the checks. We should maintain that by fixing things before actually upgrading the version we are using. In some cases I will suppress checks.

I will be making style changes to the code over a series of PRs and then updating the version. I've already done the updates locally, but I will present them in PRs that are each focused on one type of change. That should make it easy to review.

The changes I'll be making in this series are mostly adding or removing spaces, removing CR from the end of lines, and adjustments to comments. So the risk of unintentionally changing the code should be very small.