[CHORE] Avoid isDefined duplicated reference, move it to twenty-shared (#9967)

# Introduction
Avoid having multiple `isDefined` definition across our pacakges
Also avoid importing `isDefined` from `twenty-ui` which exposes a huge
barrel for a such little util function

## In a nutshell
Removed own `isDefined.ts` definition from `twenty-ui` `twenty-front`
and `twenty-server` to move it to `twenty-shared`.
Updated imports for each packages, and added explicit dependencies to
`twenty-shared` if not already in place

Related PR https://github.com/twentyhq/twenty/pull/9941

packages/twenty-front/src/testing/mock-data/index.ts

@@ -6,8 +6,7 @@ import {
   isString,
 } from '@sniptt/guards';
 import { GraphQLVariables } from 'msw';
-
-import { isDefined } from '../../utils/isDefined';
+import { isDefined } from 'twenty-shared';
 
 type StringFilter = {
   equals?: string;