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/page-layout-widget/utils/validate-widget-grid-position.util.ts

@@ -7,7 +7,7 @@ import {
   PageLayoutWidgetExceptionMessageKey,
   generatePageLayoutWidgetExceptionMessage,
 } from 'src/engine/metadata-modules/page-layout-widget/exceptions/page-layout-widget.exception';
-import { type FlatEntityValidationError } from 'src/engine/workspace-manager/workspace-migration-v2/workspace-migration-builder-v2/builders/types/failed-flat-entity-validation.type';
+import { type FlatEntityValidationError } from 'src/engine/workspace-manager/workspace-migration/workspace-migration-builder/builders/types/failed-flat-entity-validation.type';
 
 type GridPosition = {
   row: number;