[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-server/src/engine/core-modules/user/user.validate.ts

@@ -1,10 +1,11 @@
+import { isDefined } from 'twenty-shared';
+
 import { User } from 'src/engine/core-modules/user/user.entity';
-import { CustomException } from 'src/utils/custom-exception';
-import { isDefined } from 'src/utils/is-defined';
 import {
   UserException,
   UserExceptionCode,
 } from 'src/engine/core-modules/user/user.exception';
+import { CustomException } from 'src/utils/custom-exception';
 
 const assertIsDefinedOrThrow = (
   user: User | undefined | null,