[4.x] Laravel 13 support (#1443)

- Update ci.yml and composer.json
- Wrap single database tenancy trait scopes in whenBooted()
- Update SessionSeparationTest to use laravel-cache- prefix in L13
  and laravel_cache_ in <=L12. Our own prefix remains tenant_%tenant%_
  (as configured in tenancy.cache.prefix). We could update this to be
  tenant-%tenant%- from now on for consistency with Laravel's prefixes
  (changed in https://github.com/laravel/framework/pull/56172) but I'm
  not sure yet. _ seems to read a bit better but perhaps consistency
  is more important. We may change this later and it can be adjusted
  in userland easily (since it's just a config option).

.github/workflows/ci.yml

@@ -17,6 +17,7 @@ jobs:
       matrix:
         include:
         - laravel: "^12.0"
+        - laravel: "^13.0"
 
     steps:
       - name: Checkout