Drop Laravel 11, add PHP 8.5 and merge CI workflows

- Require Laravel 12 or 13 and drop orchestra/testbench 9
- Add PHP 8.5 to the test matrix
- Merge the test and PHPStan workflows into a single CI workflow,
  running PHPStan before the test matrix
- Add manual dispatch and cancel superseded runs
- Update requirements and badge in README

composer.json

@@ -19,13 +19,13 @@
     "require": {
         "php": "^8.3",
         "spatie/laravel-package-tools": "^1.16",
-        "illuminate/contracts": "^11.0||^12.0||^13.0"
+        "illuminate/contracts": "^12.0||^13.0"
     },
     "require-dev": {
         "laravel/pint": "^1.14",
         "nunomaduro/collision": "^8.1",
         "larastan/larastan": "^3.0",
-        "orchestra/testbench": "^9.0||^10.0||^11.0",
+        "orchestra/testbench": "^10.0||^11.0",
         "pestphp/pest": "^3.0||^4.0",
         "pestphp/pest-plugin-arch": "^3.0||^4.0",
         "pestphp/pest-plugin-laravel": "^3.0||^4.0",