Fix changed files action for phpcs baseline

[Tjitse-E]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/mage-os/github-actions/blob/main/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Please describe:

What is the current behavior?

Currently we use tj-actions/changed-files to extract the files changed in a PR. This caused issues in the integration testing PR: the reported changed files were invalid and not changed by the PR.

I've fixed this by using dorny/paths-filter to extract the files that need checking with PHCPcs. It's a Github action we have been using for almost a year internally at Vendic. Using dorny/paths-filter we can only filter added or modified files that match our glob.

What is the new behavior?

In addition to that I also moved the repo and ref to the action input. This allows for easier testing specific PR's if more bugs occur in the future

Does this PR introduce a breaking change?

• Yes
• No

See mage-os/mageos-magento2#59

Other information

See an example that shows the correct behaviour here.
This run:

• demonstrates that the baseline works, since the scanned file (app/code/Magento/AdminAnalytics/Model/ResourceModel/Viewer/Logger.php) contains an existing phpcs issue 24 | WARNING | Visibility must be declared on all constants if your project supports PHP 7.1 or later.
• demonstrates that the action extracts the correct files to scan for phpcs