Refactor flat entity maps to be universal oriented (#17665)

# Introduction
In preparation of the workspace agnostic builder, we're migrating
`FlatEntityMaps` to be universal identifier oriented and based
As in the builder context there're won't be any ids at all
Please also note that the FlatEntity is a UniversalFlatEntity superset

From
```ts
import { type SyncableFlatEntity } from 'src/engine/metadata-modules/flat-entity/types/flat-entity-from.type';

export type FlatEntityMaps<T extends SyncableFlatEntity> = {
  byId: Partial<Record<string, T>>;
  idByUniversalIdentifier: Partial<Record<string, string>>;
  universalIdentifiersByApplicationId: Partial<Record<string, string[]>>;
};
```

To
```ts
export type FlatEntityMaps<
  T extends SyncableFlatEntity | UniversalSyncableFlatEntity,
> = {
  byUniversalIdentifier: Partial<Record<string, T>>;
  universalIdentifierById: Partial<Record<string, string>>;
  universalIdentifiersByApplicationId: Partial<Record<string, string[]>>; // this might make more sense to be migrated to universalIdentifiersByApplicationUniversalIdentifier but it's the main topic of this PR
};
```

## Low level maps tools
Had to refactor find | create | delete | replace | find-many | get-sub
tools ( through mutations and or throw equivalent )

packages/twenty-server/src/engine/metadata-modules/flat-object-metadata/utils/build-object-id-by-name-maps.util.ts

@@ -12,15 +12,15 @@ export const buildObjectIdByNameMaps = (
   const idByNameSingular: Record<string, string> = {};
   const idByNamePlural: Record<string, string> = {};
 
-  for (const [objectId, objectMetadata] of Object.entries(
-    flatObjectMetadataMaps.byId,
+  for (const objectMetadata of Object.values(
+    flatObjectMetadataMaps.byUniversalIdentifier,
   )) {
     if (!isDefined(objectMetadata)) {
       continue;
     }
 
-    idByNameSingular[objectMetadata.nameSingular] = objectId;
-    idByNamePlural[objectMetadata.namePlural] = objectId;
+    idByNameSingular[objectMetadata.nameSingular] = objectMetadata.id;
+    idByNamePlural[objectMetadata.namePlural] = objectMetadata.id;
   }
 
   return { idByNameSingular, idByNamePlural };

packages/twenty-server/src/engine/metadata-modules/flat-object-metadata/utils/from-delete-object-input-to-flat-field-metadatas-to-delete.util.ts

@@ -78,7 +78,9 @@ export const fromDeleteObjectInputToFlatFieldMetadatasToDelete = ({
   );
 
   // TODO We should maintain a idsByObjectMetadataId in the flatIndexMaps
-  const flatIndexMetadataToDelete = Object.values(flatIndexMaps.byId).filter(
+  const flatIndexMetadataToDelete = Object.values(
+    flatIndexMaps.byUniversalIdentifier,
+  ).filter(
     (flatIndex): flatIndex is FlatIndexMetadata =>
       isDefined(flatIndex) &&
       flatIndex.objectMetadataId === flatObjectMetadataToDelete.id,

packages/twenty-server/src/engine/metadata-modules/flat-object-metadata/validators/utils/validate-flat-object-metadata-name-and-labels.util.ts

@@ -23,7 +23,7 @@ export const doesOtherObjectWithSameNameExists = ({
   objectMetadataNameSingular,
   existingObjectMetadataId,
 }: ValidateNoOtherObjectWithSameNameExistsOrThrowsParams) =>
-  Object.values(objectMetadataMaps.byId)
+  Object.values(objectMetadataMaps.byUniversalIdentifier)
     .filter(isDefined)
     .some(
       (objectMetadata) =>