Remove sync-metadata and IS_WORKSPACE_CREATION_V2_ENABLED feature flag (#16997)

# Introduction
Followup of
https://github.com/twentyhq/twenty/pull/17001#pullrequestreview-3638508738
close https://github.com/twentyhq/core-team-issues/issues/1910

We've completely decom the `sync-metadata` in production. We're now then
removing its implementation in favor of the v2.

## TODO:
- [x] Remove sync-metadata implem and commands
- [x] Remove workspace decorators 
- [x] Type each deprecated field to deprecated on their workspaceEntity
- [x] Remove the `workspace-sync-metadata` folder entirely
- [x] remove workspace migration
- [x] workspace migration removal migration
- [x] remove the `v2` references from workspace manager file names
- [x] remove the `v2` references from workspace manager modules
- [ ] Double check impact on translation file path updates


## Note
- Removed the gate logic
- Remains some service v2 naming, serverless needs to be migrated on v2
fully
- Removed workspaceMigration service app health consumption, making it
always returning up ( no more down ) cc @FelixMalfait ( quite obsolete
health check now, will require complete refactor once we introduce inter
app dependency etc )

packages/twenty-server/src/engine/metadata-modules/route-trigger/route-trigger.module.ts

@@ -13,7 +13,7 @@ import { RouteTriggerService } from 'src/engine/metadata-modules/route-trigger/r
 import { RouteTriggerV2Service } from 'src/engine/metadata-modules/route-trigger/services/route-trigger-v2.service';
 import { WorkspaceFlatRouteTriggerMapCacheService } from 'src/engine/metadata-modules/route-trigger/services/workspace-flat-route-trigger-map-cache.service';
 import { ServerlessFunctionModule } from 'src/engine/metadata-modules/serverless-function/serverless-function.module';
-import { WorkspaceMigrationV2Module } from 'src/engine/workspace-manager/workspace-migration-v2/workspace-migration-v2.module';
+import { WorkspaceMigrationModule } from 'src/engine/workspace-manager/workspace-migration/workspace-migration.module';
 
 @Module({
   imports: [
@@ -24,7 +24,7 @@ import { WorkspaceMigrationV2Module } from 'src/engine/workspace-manager/workspa
     ServerlessFunctionModule,
     WorkspaceManyOrAllFlatEntityMapsCacheModule,
     PermissionsModule,
-    WorkspaceMigrationV2Module,
+    WorkspaceMigrationModule,
   ],
   controllers: [RouteTriggerController],
   providers: [