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/ai/ai-agent/agent.service.ts

@@ -37,7 +37,7 @@ export class AgentService {
         'flatRoleTargetByAgentIdMaps',
       ]);
 
-    return Object.values(flatAgentMaps.byId)
+    return Object.values(flatAgentMaps.byUniversalIdentifier)
       .filter(isDefined)
       .map((flatAgent) => {
         const roleId = flatRoleTargetByAgentIdMaps[flatAgent.id]?.roleId;

packages/twenty-server/src/engine/metadata-modules/ai/ai-agent/utils/from-update-agent-input-to-flat-agent-to-update.util.ts

@@ -13,6 +13,7 @@ import {
 import { type UpdateAgentInput } from 'src/engine/metadata-modules/ai/ai-agent/dtos/update-agent.input';
 import { FLAT_AGENT_EDITABLE_PROPERTIES } from 'src/engine/metadata-modules/flat-agent/constants/flat-agent-editable-properties.constant';
 import { type FlatAgentMaps } from 'src/engine/metadata-modules/flat-agent/types/flat-agent-maps.type';
+import { findFlatEntityByIdInFlatEntityMaps } from 'src/engine/metadata-modules/flat-entity/utils/find-flat-entity-by-id-in-flat-entity-maps.util';
 import { type FlatAgent } from 'src/engine/metadata-modules/flat-agent/types/flat-agent.type';
 import { type FlatRoleTargetByAgentIdMaps } from 'src/engine/metadata-modules/flat-agent/types/flat-role-target-by-agent-id-maps.type';
 import { type FlatRoleTarget } from 'src/engine/metadata-modules/flat-role-target/types/flat-role-target.type';
@@ -95,7 +96,10 @@ export const fromUpdateAgentInputToFlatAgentToUpdate = ({
       ['id'],
     );
 
-  const existingFlatAgent = flatAgentMaps.byId[agentIdToUpdate];
+  const existingFlatAgent = findFlatEntityByIdInFlatEntityMaps({
+    flatEntityId: agentIdToUpdate,
+    flatEntityMaps: flatAgentMaps,
+  });
 
   if (!isDefined(existingFlatAgent)) {
     throw new AgentException(