Workspace migration v2 testing (#13136)

# Introduction
Introduced `EachTesting` pattern for the builder unit tests.
As always any suggestions are more than welcomed !


Still need to:
- [x] implem basic tests for field
- [x] create `get-flat-index-field-metadata.mock.ts`
- [x] Implement basic tests for index and index-fields
- [ ] Implem standard edges cases tests TDD style

## Misc
- was https://github.com/twentyhq/twenty/pull/13132 closed due to mess
to rebase on main

packages/twenty-shared/src/testing/index.ts

@@ -7,5 +7,6 @@
  *                              |___/
  */
 
+export { eachTestingContextFilter } from './EachTestingContextFilter';
 export type { EachTestingContext } from './types/EachTestingContext.type';
 export type { SuccessfulAndFailingTestCases } from './types/SuccessfulAndFailingTestCases';