chore(phpstan): enable phpstan in bundled extensions (#3667)

* feat(phpstan): pick up extended model relations typings
* feat(phpstan): pick up extended model date attributes
* feat(core): introduce `castAttribute` extender
Stops using `dates` as it's deprecated in laravel 8
* feat(phpstan): pick up extended model attributes through casts
* fix: extenders not resolved when declared namespace
* fix(phpstan): new model attributes are always nullable
* chore(phpstan): add helpful cache clearing command
* Apply fixes from StyleCI
* chore: improve extend files provider logic
* chore: rename `castAttribute` to just `cast`
* chore: update phpstan package to detect `cast` method
* chore: enable phpstan in bundled extensions
* chore: rebasing conflicts
* chore: rebasing conflicts
* chore: typings for latest 1.7 changes

Signed-off-by: Sami Mazouz <sychocouldy@gmail.com>

phpstan.neon

@@ -5,6 +5,34 @@ parameters:
 	level: 5
 	paths:
 	  - framework/core/src
+	  - extensions/akismet/src
+	  - extensions/akismet/extend.php
+	  - extensions/approval/src
+	  - extensions/approval/extend.php
+	  - extensions/flags/src
+	  - extensions/flags/extend.php
+	  - extensions/likes/src
+	  - extensions/likes/extend.php
+	  - extensions/lock/src
+	  - extensions/lock/extend.php
+	  - extensions/mentions/src
+	  - extensions/mentions/extend.php
+	  - extensions/nicknames/src
+	  - extensions/nicknames/extend.php
+	  - extensions/package-manager/src
+	  - extensions/package-manager/extend.php
+	  - extensions/pusher/src
+	  - extensions/pusher/extend.php
+	  - extensions/statistics/src
+	  - extensions/statistics/extend.php
+	  - extensions/sticky/src
+	  - extensions/sticky/extend.php
+	  - extensions/subscriptions/src
+	  - extensions/subscriptions/extend.php
+	  - extensions/suspend/src
+	  - extensions/suspend/extend.php
+	  - extensions/tags/src
+	  - extensions/tags/extend.php
 	excludePaths:
 		- *.blade.php
 	checkMissingIterableValueType: false