chore: update checkstyle plugin to 3.6.0

[kstribrnAmzn]

Issue #, if available:
No issue. I was simply annoyed that I had to build the code to run checkstyle checks. This PR allows the checks to be ran through the Checkstyle-Idea plugin.

Description of changes:
The maven checkstyle plugin version 3.6.0
is the latest version of the plugin and supports
newer checkstyle versions. This commit bumps
checkstyle to the latest version (10.3.4) and
fixes violations.

Why is this change necessary:
Simplifies development work by allowing checks to be performed while developing.

How was this change tested:

• Updated or added new unit tests.
• Updated or added new integration tests.
• Updated or added new end-to-end tests.
• If my code makes a remote network call, it was tested with a proxy.

Any additional information or context required to review the change:
You can install Checkstyle-Idea plugin and try out the configuration.

Documentation Checklist:

• Updated the README if applicable.

Compatibility Checklist:

• I confirm that the change is backwards compatible.
• Any modification or deletion of public interfaces does not impact other plugin components.
• For external library version updates, I have reviewed its change logs and Nucleus does not consume
  any deprecated method or type.

Refer to Compatibility Guidelines for more information.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.