feat(core): Add user.profile.beforeUpdate hook

[tomi]

Summary

Add user.profile.beforeUpdate hook so we can prevent user email change if it overlaps with other users email.

Related tickets and issues

https://github.com/n8n-io/n8n-cloud/pull/903

https://linear.app/n8n/issue/ADO-1248/feature-prevent-users-from-updating-email-if-it-already-exists-in

Review / Merge checklist

• [ ] PR title and summary are descriptive. Remember, the title automatically goes into the changelog. Use (no-changelog) otherwise. (conventions)
• [ ] Docs updated or follow-up ticket created.
• [ ] Tests included.

  A bug is not considered fixed, unless a test is added to prevent it from happening again. A feature is not complete without tests.