chore: remove all actions references

[ali-kafel]

Summary

The action defined in this repo is not used anywhere. We are mainly only referencing the checkstyle configurations in downstream repositories. We are removing all references to the unused action.

Detail

Removal of GitHub Action and related files:

• Deleted the Dockerfile, which previously set up the environment for running Checkstyle and Reviewdog.
• Removed the GitHub Action definition from action.yml, including all inputs and Docker configuration.
• Deleted the entrypoint.sh script that executed Checkstyle and piped results to Reviewdog.

Documentation update:

• Updated README.md to reflect the new purpose of the repository, focusing on providing Checkstyle configurations rather than an action.

Testing

No testing needed we are simply only referencing the already existing checkstyle configs. I checked all repos and we are not using the action anywhere.

Documentation

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Requested Reviewers: @mention

[creilly12]

Thank you.

Confirmed not in use. This was a review bot that didn't pan out.