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-role-target/utils/find-flat-role-target-from-foreign-key.util.ts

@@ -13,9 +13,9 @@ export const findFlatRoleTargetFromForeignKey = ({
   targetMetadataForeignKey,
   targetId,
 }: FindAllFlatRoleTargetOfArgs): FlatRoleTarget | undefined => {
-  const allRoleTargets = Object.values(flatRoleTargetMaps.byId).filter(
-    isDefined,
-  );
+  const allRoleTargets = Object.values(
+    flatRoleTargetMaps.byUniversalIdentifier,
+  ).filter(isDefined);
 
   return allRoleTargets.find(
     (roleTarget) => roleTarget[targetMetadataForeignKey] === targetId,