Common - Remove feature flag (#15371)

To be done in an other PR, move graphql-query-runner handlers in
common-api-query-runner folder (+ renaming + typing improvments)


Fixes : 
- totalCount on findMany (Rest)
- getAllSelectedFields did not handle composite field (Rest)
- issue with endCursor (Rest)
- args processing for updateOne and createOne (Rest + Gql)
- fix findDuplicates (Gql)

packages/twenty-server/src/engine/core-modules/feature-flag/enums/feature-flag-key.enum.ts

@@ -19,6 +19,5 @@ export enum FeatureFlagKey {
   IS_PUBLIC_DOMAIN_ENABLED = 'IS_PUBLIC_DOMAIN_ENABLED',
   IS_EMAILING_DOMAIN_ENABLED = 'IS_EMAILING_DOMAIN_ENABLED',
   IS_DYNAMIC_SEARCH_FIELDS_ENABLED = 'IS_DYNAMIC_SEARCH_FIELDS_ENABLED',
-  IS_COMMON_API_ENABLED = 'IS_COMMON_API_ENABLED',
   IS_WORKFLOW_RUN_STOPPAGE_ENABLED = 'IS_WORKFLOW_RUN_STOPPAGE_ENABLED',
 }