[7.x] Statamic 5 - Githubissues

This pull request makes the necessary changes required to support Statamic 5.

This PR will be added to as time goes on.

Changes

Updates the version constraint in composer.json
- Changed to dev-master for now. Once v5 has been released, it can be changed to ^5.0.
Adjusted testing matrix
Replaces laravel/helpers functions
- Statamic 5 dropped the laravel/helpers dependency, which provided backwards compatibility for old string/array helpers.
- We were using some of the helpers provided by this package, so I've replaced them with calls to Laravel's Str class.
Simplifies the TestCase
- This was made possible by https://github.com/statamic/cms/pull/9573.
Fixed broken Ignition solutions.
Changed how we call the Antlers parser in SendConfiguredNotifications
- Previously, we were directly calling the Regex parser. However, the Regex Parser has been removed in Statamic 5 so this updates the code to call Antlers::parser() instead.
Changed how we get a database table's columns
- Laravel 11 removed its doctrine/dbal dependency but it provided alternative methods for everything it was providing, so we've adjusted our code to use it.

[x] Investigate failing order notification tests
[x] Adjust version constraints in composer.json & testing matrix to released versions, rather than dev-* versions.