Refactor onboarding user vars to be absent when user is fully onboarded (#6531)

In this PR:
- take feedbacks from: https://github.com/twentyhq/twenty/pull/6530 /
https://github.com/twentyhq/twenty/pull/6529 /
https://github.com/twentyhq/twenty/pull/6526 /
https://github.com/twentyhq/twenty/pull/6512
- refactor onboarding uservars to be absent when the user is fully
onboarded: isStepComplete ==> isStepIncomplete
- introduce a new workspace.activationStatus: CREATION_ONGOING

I'm retesting the whole flow:
- with/without BILLING
- sign in with/without SSO
- sign up with/without SSO
- another workspaceMembers join the team
- subscriptionCanceled
- access to billingPortal

packages/twenty-front/src/modules/ui/layout/states/ShowPageRecoilScopeContext.ts

@@ -1,4 +0,0 @@
-import { createContext } from 'react';
-
-/* istanbul ignore next */
-export const ShowPageRecoilScopeContext = createContext<string | null>(null);