Introducing view field group syncable entity (#17867)

## Context
Introduces a new viewFieldGroup entity that allows grouping view fields
into sections (e.g. "General", "Additional", "Other") within a view.

The page layout fields widget needs a way to organize fields into
sections. Today, views have no concept of field grouping. This PR
introduces the viewFieldGroup entity which sits between a view and its
viewFields, enabling section-based organization.

<img width="401" height="724" alt="Layout - V2 (customize visibility)"
src="https://github.com/user-attachments/assets/6376e2ab-44db-42bf-9d2c-758f56f6b548"
/>

---------

Co-authored-by: Charles Bochet <charles@twenty.com>

packages/twenty-shared/src/metadata/all-metadata-name.constant.ts

@@ -3,6 +3,7 @@ export const ALL_METADATA_NAME = {
   objectMetadata: 'objectMetadata',
   view: 'view',
   viewField: 'viewField',
+  viewFieldGroup: 'viewFieldGroup',
   viewGroup: 'viewGroup',
   rowLevelPermissionPredicate: 'rowLevelPermissionPredicate',
   rowLevelPermissionPredicateGroup: 'rowLevelPermissionPredicateGroup',