Modernize developer experience (npm, Node, Composer, Grunt, wp/scripts)

[jeffpaul]

The goal of this project is to clean up and update each 10up managed extension's npm dependencies to remove outdated packages. Additionally, we need to upgrade the Node.js version that is consistent with WooCommerce. The update process should include thorough testing to verify functionality and compatibility with the updated dependencies and Node.js version.

• Upgrade to npm 10 (8 as a minimum)
• Upgrade to Node 20 (including GitHub Actions)
• Update Node dependencies to current major versions
• Update Composer dependencies to current major versions
• Replace Grunt build processes with @wordpress/scripts
• Document npm, Node, Composer, @wordpress/scripts usage and versions in README.md

After upgrading npm/Node versions and replacing Grunt, we will ensure that e2e tests and overall plugin functionality continues to work as expected via regression testing following defined critical flows.

Project success metrics:

• Developer local versions are declared in the project readme file
• Extension builds properly with defined scripts and pass tests (E2E, Unit, QIT)
• PR(s) merged to trunk
• Release ZIP created and tagged for release