v2.13.0: Fix Castables issue #1312 (#1388)

Fixes

• Fix return type of methods provided by SoftDeletes #1345 / KentarouTakeda
• Handle PHP 8.1 deprecation warnings when passing null to new \ReflectionClass #1351 / mfn
• Fix issue where \Eloquent is not included when using write_mixin #1352 / Jefemy
• Fix model factory method arguments for Laravel >= 9 #1361 / wimski
• Improve return type of mock helper methods in tests #1405 / bentleyo
• Fix Castable class if failed to detect it from return types #1388 / kwarcu

Added

• Added Laravel 10 support #1407 / lptn
• Add support for custom casts that implement CastsInboundAttributes #1329 / sforward
• Add option use_generics_annotations for collection type hints #1298 / tanerkay