Files v2 - Add new FILES field type (#17236)

In this PR : 
- New field type FieldMetadataType.FILES added (as jsonb in DB)
- Backend: GraphQL types, validation, REST API schema, data processor
handling
- Frontend: field configuration in settings
- Feature flag IS_FILES_FIELD_ENABLED to gate the feature
- Integration tests for create/filter validation
- Dev seed: Feature flag enabled + FILES field on survey result object


To do in next PRs : 
- Backend : 
-- new workspaceFile controller (for download) & new workspaceFile
upload resolver (for upload)
-- pre-hook/post-hook to ensure fileId existence + listener to ensure
cleaning
- Frontend : FILES field display/edit in table view, record, ...

packages/twenty-front/src/modules/object-record/utils/generateEmptyFieldValue.ts

@@ -123,6 +123,9 @@ export const generateEmptyFieldValue = ({
     case FieldMetadataType.TS_VECTOR: {
       return null;
     }
+    case FieldMetadataType.FILES: {
+      return null;
+    }
     default: {
       return assertUnreachable(
         fieldMetadataItem.type,