Unify user update methods (#28733)

Fixes #28660
Fixes an admin api bug related to `user.LoginSource`
Fixed `/user/emails` response not identical to GitHub api

This PR unifies the user update methods. The goal is to keep the logic
only at one place (having audit logs in mind). For example, do the
password checks only in one method not everywhere a password is updated.

After that PR is merged, the user creation should be next.

models/fixtures/email_address.yml

@@ -285,3 +285,11 @@
   lower_email: abcde@gitea.com
   is_activated: true
   is_primary: false
+
+-
+  id: 37
+  uid: 37
+  email: user37@example.com
+  lower_email: user37@example.com
+  is_activated: true
+  is_primary: true

models/fixtures/user.yml

@@ -1095,7 +1095,7 @@
   allow_git_hook: false
   allow_import_local: false
   allow_create_organization: true
-  prohibit_login: true
+  prohibit_login: false
   avatar: avatar29
   avatar_email: user30@example.com
   use_custom_avatar: false
@@ -1332,3 +1332,40 @@
   repo_admin_change_team_access: false
   theme: ""
   keep_activity_private: false
+
+-
+  id: 37
+  lower_name: user37
+  name: user37
+  full_name: User 37
+  email: user37@example.com
+  keep_email_private: false
+  email_notifications_preference: enabled
+  passwd: ZogKvWdyEx:password
+  passwd_hash_algo: dummy
+  must_change_password: false
+  login_source: 0
+  login_name: user37
+  type: 0
+  salt: ZogKvWdyEx
+  max_repo_creation: -1
+  is_active: true
+  is_admin: false
+  is_restricted: false
+  allow_git_hook: false
+  allow_import_local: false
+  allow_create_organization: true
+  prohibit_login: true
+  avatar: avatar29
+  avatar_email: user37@example.com
+  use_custom_avatar: false
+  num_followers: 0
+  num_following: 0
+  num_stars: 0
+  num_repos: 0
+  num_teams: 0
+  num_members: 0
+  visibility: 0
+  repo_admin_change_team_access: false
+  theme: ""
+  keep_activity_private: false