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/flat-agent/utils/transform-standard-agent-definition-to-flat-agent.util.ts

@@ -1,35 +0,0 @@
-import { v4 } from 'uuid';
-
-import { type AgentEntity } from 'src/engine/metadata-modules/ai/ai-agent/entities/agent.entity';
-import { type FlatAgent } from 'src/engine/metadata-modules/flat-agent/types/flat-agent.type';
-import { type StandardAgentDefinition } from 'src/engine/workspace-manager/workspace-sync-metadata/standard-agents/types/standard-agent-definition.interface';
-
-export const transformStandardAgentDefinitionToFlatAgent = ({
-  standardAgentDefinition,
-  workspaceId,
-  existingAgentEntity,
-}: {
-  standardAgentDefinition: StandardAgentDefinition;
-  workspaceId: string;
-  existingAgentEntity?: Pick<
-    AgentEntity,
-    'createdAt' | 'deletedAt' | 'updatedAt' | 'id'
-  >;
-}): FlatAgent => {
-  const {
-    standardRoleId: _standardRoleId,
-    outputStrategy: _outputStrategy,
-    ...agentData
-  } = standardAgentDefinition;
-  const createdAt = new Date().toISOString();
-
-  return {
-    id: existingAgentEntity?.id ?? v4(),
-    createdAt: existingAgentEntity?.createdAt?.toISOString() ?? createdAt,
-    updatedAt: existingAgentEntity?.updatedAt?.toISOString() ?? createdAt,
-    deletedAt: existingAgentEntity?.deletedAt?.toISOString() ?? null,
-    ...agentData,
-    workspaceId,
-    universalIdentifier: standardAgentDefinition.standardId,
-  };
-};