Move view in metadata-modules/ and create atomic folder + module for each view entity (#14990)

# Introduction
Preparing view-filter and view-group introduction in v2 core engine
Moving view from `core-modules` to `metadata-modules`

## What happened

### Created dedicated modules for each view entity:
- ViewFieldModule
- ViewFilterModule
- ViewFilterGroupModule
- ViewGroupModule
- ViewSortModule

### Each module is now completely independent with its own:
- Controller
- Resolver
- Service
- Entity

### Created dedicated abstraction metadata module folder for:
- flat-view-field
- flat-view

### Dependencies 
- Eleminated circular dep on ViewModule to all others ones
- Granular import not importing the whole viewModule anymore everywhere


close https://github.com/twentyhq/core-team-issues/issues/1703

packages/twenty-server/src/engine/metadata-modules/flat-view/flat-view.module.ts

@@ -0,0 +1,12 @@
+import { Module } from '@nestjs/common';
+import { TypeOrmModule } from '@nestjs/typeorm';
+
+import { WorkspaceFlatViewMapCacheService } from 'src/engine/metadata-modules/flat-view/services/workspace-flat-view-map-cache.service';
+import { ViewEntity } from 'src/engine/metadata-modules/view/entities/view.entity';
+
+@Module({
+  imports: [TypeOrmModule.forFeature([ViewEntity])],
+  providers: [WorkspaceFlatViewMapCacheService],
+  exports: [WorkspaceFlatViewMapCacheService],
+})
+export class FlatViewModule {}