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/dataloaders/dataloader.service.ts

@@ -16,6 +16,7 @@ import { RelationDTO } from 'src/engine/metadata-modules/field-metadata/dtos/rel
 import { type FieldMetadataEntity } from 'src/engine/metadata-modules/field-metadata/field-metadata.entity';
 import { resolveFieldMetadataStandardOverride } from 'src/engine/metadata-modules/field-metadata/utils/resolve-field-metadata-standard-override.util';
 import { WorkspaceManyOrAllFlatEntityMapsCacheService } from 'src/engine/metadata-modules/flat-entity/services/workspace-many-or-all-flat-entity-maps-cache.service';
+import { findFlatEntityByIdInFlatEntityMaps } from 'src/engine/metadata-modules/flat-entity/utils/find-flat-entity-by-id-in-flat-entity-maps.util';
 import { findFlatEntityByIdInFlatEntityMapsOrThrow } from 'src/engine/metadata-modules/flat-entity/utils/find-flat-entity-by-id-in-flat-entity-maps-or-throw.util';
 import { findManyFlatEntityByIdInFlatEntityMapsOrThrow } from 'src/engine/metadata-modules/flat-entity/utils/find-many-flat-entity-by-id-in-flat-entity-maps-or-throw.util';
 import { findAllOthersMorphRelationFlatFieldMetadatasOrThrow } from 'src/engine/metadata-modules/flat-field-metadata/utils/find-all-others-morph-relation-flat-field-metadatas-or-throw.util';
@@ -458,7 +459,10 @@ export class DataloaderService {
 
       return dataLoaderParams.map(
         ({ indexMetadata: { id: indexMetadataId } }) => {
-          const indexMetadataEntity = flatIndexMaps.byId[indexMetadataId];
+          const indexMetadataEntity = findFlatEntityByIdInFlatEntityMaps({
+            flatEntityId: indexMetadataId,
+            flatEntityMaps: flatIndexMaps,
+          });
 
           if (!isDefined(indexMetadataEntity)) {
             return [];
@@ -498,8 +502,10 @@ export class DataloaderService {
         );
 
       return dataLoaderParams.map((dataLoaderParam) => {
-        const flatObjectMetadata =
-          flatObjectMetadataMaps.byId[dataLoaderParam.objectMetadataId];
+        const flatObjectMetadata = findFlatEntityByIdInFlatEntityMaps({
+          flatEntityId: dataLoaderParam.objectMetadataId,
+          flatEntityMaps: flatObjectMetadataMaps,
+        });
 
         if (!isDefined(flatObjectMetadata)) {
           return null;