Add changie-validation job to lint workflow

* Add new job `changie-validation` to check for changie entries in `.changes/unreleased` directory
* Skip `changie-validation` job if `.changes` directory does not exist or if labels `no-changie-required` or `dependencies` are set
* Replace deprecated `set-output` command with `echo "{name}={value}" >> $GITHUB_OUTPUT`
* Add comments using the gh cli for changie validation results
* Use command to list changes in this pull request and confirm `.changes/unreleased` has files included that are added/changed
* If changie entry is required, use `gh pr review <PR_NUMBER> --request-changes --body "Explanation for changes needed"`
* If changie entry is not required, use `gh pr review <PR_NUMBER> --comment --body "General comment"`