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/metadata-engine.module.ts

@@ -17,7 +17,6 @@ import { ServerlessFunctionModule } from 'src/engine/metadata-modules/serverless
 import { SkillModule } from 'src/engine/metadata-modules/skill/skill.module';
 import { ViewModule } from 'src/engine/metadata-modules/view/view.module';
 import { WorkspaceMetadataVersionModule } from 'src/engine/metadata-modules/workspace-metadata-version/workspace-metadata-version.module';
-import { WorkspaceMigrationModule } from 'src/engine/metadata-modules/workspace-migration/workspace-migration.module';
 
 @Module({
   imports: [
@@ -33,7 +32,6 @@ import { WorkspaceMigrationModule } from 'src/engine/metadata-modules/workspace-
     AiChatModule,
     ViewModule,
     WorkspaceMetadataVersionModule,
-    WorkspaceMigrationModule,
     RoleModule,
     PermissionsModule,
     RouteTriggerModule,