[5.x] Ensure install:broadcasting is run when installing into Laravel 11 application

[duncanmcclean]

This pull request fixes an issue in our php please install:collaboration command, where Laravel's install:broadcasting command wasn't being run, causing things like its config and routing files to not be published.

It seems like this was caused by the BroadcastServiceProvider always being part of the app's loaded service providers, even if Laravel's install:broadcasting command hasn't been run.

This PR fixes it by simply checking for the existence of the broadcasting.php config file, which is created as part of the install:broadcasting command.

Fixes statamic/collaboration#101.

[jasonvarga]

Does this still work on Laravel 10? I think we had it the way it was because it "worked" across both versions.

[duncanmcclean]

Does this still work on Laravel 10? I think we had it the way it was because it "worked" across both versions.

Good catch!

The check I've changed checks if that the install:broadcasting command hasn't already been run, which is only useful for Laravel 11 applications.

For Laravel 10 applications, we have a version_compare check. I've just moved that to before the L11 check, otherwise, it wouldn't get hit since they all have the broadcasting.php config.