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-page-layout/utils/from-destroy-page-layout-input-to-flat-page-layout-or-throw.util.ts

@@ -5,6 +5,7 @@ import {
 } from 'twenty-shared/utils';
 
 import { type FlatPageLayoutMaps } from 'src/engine/metadata-modules/flat-page-layout/types/flat-page-layout-maps.type';
+import { findFlatEntityByIdInFlatEntityMaps } from 'src/engine/metadata-modules/flat-entity/utils/find-flat-entity-by-id-in-flat-entity-maps.util';
 import { type FlatPageLayout } from 'src/engine/metadata-modules/flat-page-layout/types/flat-page-layout.type';
 import {
   PageLayoutException,
@@ -27,7 +28,10 @@ export const fromDestroyPageLayoutInputToFlatPageLayoutOrThrow = ({
     ['id'],
   );
 
-  const existingFlatPageLayoutToDestroy = flatPageLayoutMaps.byId[pageLayoutId];
+  const existingFlatPageLayoutToDestroy = findFlatEntityByIdInFlatEntityMaps({
+    flatEntityId: pageLayoutId,
+    flatEntityMaps: flatPageLayoutMaps,
+  });
 
   if (!isDefined(existingFlatPageLayoutToDestroy)) {
     throw new PageLayoutException(

packages/twenty-server/src/engine/metadata-modules/flat-page-layout/utils/from-update-page-layout-input-to-flat-page-layout-to-update-or-throw.util.ts

@@ -5,6 +5,7 @@ import {
 } from 'twenty-shared/utils';
 
 import { FLAT_PAGE_LAYOUT_EDITABLE_PROPERTIES } from 'src/engine/metadata-modules/flat-page-layout/constants/flat-page-layout-editable-properties.constant';
+import { findFlatEntityByIdInFlatEntityMaps } from 'src/engine/metadata-modules/flat-entity/utils/find-flat-entity-by-id-in-flat-entity-maps.util';
 import { type FlatPageLayoutMaps } from 'src/engine/metadata-modules/flat-page-layout/types/flat-page-layout-maps.type';
 import { type FlatPageLayout } from 'src/engine/metadata-modules/flat-page-layout/types/flat-page-layout.type';
 import { type UpdatePageLayoutInput } from 'src/engine/metadata-modules/page-layout/dtos/inputs/update-page-layout.input';
@@ -31,8 +32,10 @@ export const fromUpdatePageLayoutInputToFlatPageLayoutToUpdateOrThrow = ({
     ['id'],
   );
 
-  const existingFlatPageLayoutToUpdate =
-    flatPageLayoutMaps.byId[pageLayoutToUpdateId];
+  const existingFlatPageLayoutToUpdate = findFlatEntityByIdInFlatEntityMaps({
+    flatEntityId: pageLayoutToUpdateId,
+    flatEntityMaps: flatPageLayoutMaps,
+  });
 
   if (!isDefined(existingFlatPageLayoutToUpdate)) {
     throw new PageLayoutException(

packages/twenty-server/src/engine/metadata-modules/flat-page-layout/utils/reconstruct-flat-page-layout-with-tabs-and-widgets.util.ts

@@ -23,7 +23,7 @@ export const reconstructFlatPageLayoutWithTabsAndWidgets = ({
   flatPageLayoutTabMaps: FlatPageLayoutTabMaps;
   flatPageLayoutWidgetMaps: FlatPageLayoutWidgetMaps;
 }): FlatPageLayoutWithTabsAndWidgets => {
-  const tabs = Object.values(flatPageLayoutTabMaps.byId)
+  const tabs = Object.values(flatPageLayoutTabMaps.byUniversalIdentifier)
     .filter(isDefined)
     .filter(
       (tab) => tab.pageLayoutId === layout.id && !isDefined(tab.deletedAt),
@@ -31,7 +31,9 @@ export const reconstructFlatPageLayoutWithTabsAndWidgets = ({
     .sort((a, b) => (a.position ?? 0) - (b.position ?? 0));
 
   const tabsWithWidgets: FlatPageLayoutTabWithWidgets[] = tabs.map((tab) => {
-    const widgets = Object.values(flatPageLayoutWidgetMaps.byId)
+    const widgets = Object.values(
+      flatPageLayoutWidgetMaps.byUniversalIdentifier,
+    )
       .filter(isDefined)
       .filter(
         (widget) =>