Remove MongoDB support

- Remove base_model configuration from workflows.php
- Update all model classes to directly extend Illuminate\Database\Eloquent\Model
- Remove class_alias logic from WorkflowServiceProvider
- Remove tests/classAliases.php file
- Update phpstan.neon to remove reference to classAliases.php
- Update WorkflowsConfigTest to remove base_model assertion

Author: rmcdaniel

src/Models/StoredWorkflow.php

@@ -5,12 +5,12 @@
 namespace Workflow\Models;
 
 use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Prunable;
 use Illuminate\Database\Eloquent\Relations\BelongsToMany;
 use Spatie\ModelStates\HasStates;
 use Workflow\States\WorkflowContinuedStatus;
 use Workflow\States\WorkflowStatus;
-use Illuminate\Database\Eloquent\Model;
 use Workflow\WorkflowStub;
 
 class StoredWorkflow extends Model