[Requires "warm" cache flush (no immediate downtime before flush)] Migrate viewGroup.fieldMetadataId -> view.mainGroupByFieldMetadataId (1/3) (#16206)

In this PR (1/3)
- introduce view.mainGroupByFieldMetadataId as the new reference
determining which fieldMetadataId is used in a grouped view, in order to
deprecate viewGroup.fieldMetadataId which creates inconsistencies.
view.mainGroupByFieldMetadataId is now filled at every view creation,
though not in use yet.
- Introduce a command to backfill view.mainGroupByFieldMetadataId for
existing views + delete all viewGroup.fieldMetadataId with a
fieldMetadataId that is not view.mainGroupByFieldMetadataId. (It should
concern 37 active workspaces)
- Temporarily disable the option to change a grouped view's
fieldMetadataId as for now it creates inconsistencies. This feature can
be reintroduced when we have done the full migration.

In a next PR
- (2/3) use view.mainGroupByFieldMetadataId instead of
viewGroup.fieldMetadataId. In FE we may keep viewGroup.fieldMetadataId
as a state (TBD). View groups will now be created / deleted as a side
effect of view's mainGroupByFieldMetadataId update.
- (3/3) remove viewGroup.fieldMetadataId

---------

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

packages/twenty-server/src/engine/core-modules/application/constants/standard-object.constant.ts

@@ -1443,6 +1443,9 @@ export const STANDARD_OBJECTS = {
         universalIdentifier:
           VIEW_STANDARD_FIELD_IDS.kanbanAggregateOperationFieldMetadataId,
       },
+      mainGroupByFieldMetadataId: {
+        universalIdentifier: VIEW_STANDARD_FIELD_IDS.mainGroupByFieldMetadataId,
+      },
       position: { universalIdentifier: VIEW_STANDARD_FIELD_IDS.position },
       isCompact: { universalIdentifier: VIEW_STANDARD_FIELD_IDS.isCompact },
       openRecordIn: {