Composer: Add composer phpcbf and composer-phpcbf-tests commands

[n7studios]

Summary

Registers additional commands in the scripts section of Composer, which serve as shorthand commands for testing and other common tasks performed in development, which were missing in #834

Command	Description
phpcbf	Runs PHP CodeSniffer on the entire plugin codebase, automatically fixing errors
phpcbf-tests	Runs PHP CodeSniffer specifically on the tests directory using test-specific standards, automatically fixing errors

Testing

Existing tests pass

Checklist

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

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