chore: load 2fa status for user search when needed (#6727)

- Don't make an extra database call to gather the 2FA status of the users returned from the search. Only load it for the admin's user list page.
- Integration testing added.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6727
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

models/user/search.go

@@ -40,6 +40,7 @@ type SearchUserOptions struct {
 	IsProhibitLogin    optional.Option[bool]
 	IncludeReserved    bool
 
+	Load2FAStatus     bool
 	ExtraParamStrings map[string]string
 }