Fix Laravel rule filtering

[GeniJaho]

When filtering the rules in the Find Rule page, the Laravel group only shows 38 rules, while there are 76 available at the moment. That happens because we only show and count the Laravel rules that belong to a set, as with the rest of the Rector groups.
That leaves out most of the Laravel rules.

In this PR we:

• Add an exception when filtering by Group, to check if the rule class starts with RectorLaravel
• Add RuleFilterTest to cover the edge case
• Use dev-main for the Laravel Rector rules, since rules can be available before we do a release
• Add the LARAVEL group name and replaces the string literal uses

Let me know please if this is OK or I need to change something.
And thank you for making the code open for the Rector website. 😄

[TomasVotruba]

Wow, this looks very good. Thanks for the test as well 🙏

I've made the CI run now...