[10.x] Fixes Model::isDirty() when AsCollection or AsEncryptedCollection have arguments

[nunomaduro]

This pull request addresses the issue with Model::isDirty() when using AsCollection or AsEncryptedCollection casters with arguments.

The problem arises when declaring the cast as AsCollection::class . ':' . CustomCollection::class, which generates a string that misleads Model::originalIsEquivalent into incorrectly evaluating the caster's behavior within a specific if condition:

// Cast: Illuminate\Database\Eloquent\Casts\AsCollection:Illuminate\Tests\Database\CustomCollection
// Before:
in_array($this->getCasts()[$key], [AsEncryptedArrayObject::class, AsEncryptedCollection::class]) // false...

// After:
Str::startsWith($this->getCasts()[$key], [AsEncryptedArrayObject::class, AsEncryptedCollection::class]) // true...