Allow usage as wp cli package

[laborin]

Description

This PR adds the ability to use the plugin as a global WP-CLI Package, to make all GF CLI commands available to any site installed on the server without the need of installing the plugin on each site.

Closes https://github.com/gravityforms/backlog/issues/3983
Closes https://github.com/gravityforms/backlog/issues/3039 by updating the "Tested up to" version

Testing instructions

1. Download this branch as a ZIP file from Github, not the package built with HAL because it removes the composer.json file.
2. Using the command line, install the plugin as a global WP-CLI Package with this command: wp package install <full path to the zip file>
   a. What location should I be at? installed from within local/site/app/public (site didn't have gravityforms repo) and it installed to /Users/gosiapado/.wpcli/packages/local/gravityforms-gravityformscli
3. Using the command line, change directory to a directory containing a WordPress site with Gravity Forms installed but NO gravityformscli installed.
   a. What location should I be at? any directory that is child of the root directory (any child of the directory containing your wp-config.php file)
4. Try using a GF Cli command and confirm it works. For example, this should list all the forms: wp gf form list

Note: Once this PR is merged, users will be able to install this package directly from the public Git repository this way:
wp package install https://github.com/gravityforms/gravityformscli.git

QA issue tracking sheet

Screenshots

Checklist:

• I've checked the error log to ensure my code doesn't throw any errors.
• I've added a changelog entry (if necessary) and updated the version number in 4 places, run npm install and committed package-lock.json (if necessary).
• My code follows the WordPress coding standards and inline documentation standards
• My code follows the accessibility standards.
• This PR has a related issue.
• This PR has a related test.
• I have given QA direction on which areas are most important to test.
• I have considered what will happen when an existing user updates to this branch.
• I have added a "Documentation Needed" label to this PR (if necessary).

[gosiapado]

@laborin, I need more details in the testing instructions, please. My local environment has multiple sites set up. I'm not sure where I'm supposed to be installing to/running commands from. I've added some subpoints with questions on no. 2 & 3 in testing instructions. Please provide examples or let me know when you're available and we can do a screenshare (or record one for me). Thank you!

[gosiapado]

With guidance was able to install package at global level and test with multiple local sites. Besides listing forms also successfully added fields to forms using the CLI. 👍
Assuming, the warning about testing and minimum tested version on the wordpress.org page won't be resolved until this is merged and published.

[morganisok]

🎉