Update composer dependencies to work with both PHP 7.4 and 8

[coreymckrill]

Also:

• Update the minimum PHP version for the plugin to 7.4, and update the "tested up to" values
• Make the plugin description consistent
• Move the woocommerce/* composer dependencies to require-dev

The dependency that was blocking compatibility with PHP 7.4 wasfakerphp/faker, because starting in v1.17.0 its own symfony/deprecation-contracts dependency changed its version requirement to ^2.2 || ^3.0. 2.2 is compatible with PHP 7.4 but 3.0 requires a minimum of 8.0.2. By specifying 2.2 as our own dependency we can ensure that version gets installed.

How to test the changes in this Pull Request:

1. Make sure you are running PHP 7.4. Try running each of the generator CLI commands and make sure there are no errors.
2. Switch to PHP 8.0 and do the same tests.
3. Switch to PHP 8.1 and do the same tests.

Changelog entry

Update minimum PHP version to 7.4, and ensure the plugin is also compatible with 8.0 and 8.1.

FOR PR REVIEWER ONLY:

• [ ] I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.