[6.x] Fixed breaking compatability with multi-schema postgres

[raymondtri]

This extends #30555 with added suggestions from Taylor Otwell regarding handling strings or arrays, while persisting the old method signature to make it non-breaking.

[mfn]

TODO

• If PR gets merged, add the new configuration option to https://github.com/laravel/laravel/blob/master/config/database.php

[driesvints]

@mfn think this one can just be documented? Don't feel it's necessary to add every single config option to the config file?

[driesvints]

Or it can be. I'm a bit indifferent tbh.

[mfn]

😄

IMHO it's most easily discovered when it's already parts of the blueprint configuration 🤷‍♀️