fix(user): Updating user info when authenticating with external IDP (#11046)

# Which Problems Are Solved

User profile updates were not propagated when using External OIDC IDP +
Login V2

# How the Problems Are Solved

* `UpdateHumanUserRequest` is added to
`RetrieveIdentityProviderIntentResponse`
* `UpdateHumanUserRequest` is returned in the
`RetrieveIdentityProviderIntentResponse` when the user already exists
during external IDP auth, which is then used in the frontend to update
the user info

# Additional Changes

* Moved integration tests related to user intent to a separate test file
* Fix redirection after external IDP user registration

# Additional Context
- Closes #10838
- Follow up: https://github.com/zitadel/zitadel/issues/11053

---------

Co-authored-by: Max Peintner <peintnerm@gmail.com>
(cherry picked from commit d7e9eddb76)

proto/zitadel/user/v2/user_service.proto

@@ -3093,6 +3093,7 @@ message RetrieveIdentityProviderIntentResponse{
     }
   ];
   AddHumanUserRequest add_human_user = 4;
+  UpdateHumanUserRequest update_human_user = 5;
 }
 
 message AddIDPLinkRequest{