Update dependencies and update to reflect new PHP Parser changes.

[BusterNeece]

This PR changes the following:

• Updates composer.json to depend on nikic/php-parser version 5.x instead of 4.x
• Bump the minimum PHP version from 7.2 to 7.4 (php-parser itself only supports 7.4 and up)
• Bump the versions of the testing dependencies
• Update factory instantiation to reflect php-parser's new syntax
• Slightly update how comments are parsed to handle changes in the parser

[oscarotero]

Thanks!
I just left a couple of comments to fix a bug regarding numeric arguments.

[BusterNeece]

@oscarotero Issues with numeric args should be fixed now. I initially couldn't tell what was causing that, but it turns out it was a simple problem with a simple fix.

[BusterNeece]

@oscarotero Just pushed an update that should fix the GitHub Actions, setting them to run from 7.4 up, and downgrading PHPUnit to the latest stable version that supports that far back. You could certainly set the minimum PHP requirement higher, but I wanted to have as few BC breaks as possible in the PR.

[oscarotero]

Great work!
Thank you!