Append an "Unrestricted users" rule to CheckUser, ContextSwitching and Impersonation plugins
Currently, we can restrict identities usage by setting a rule like ''!$anonymous''.
This rule is based on used or checked identity not on user. And this rule is checked for all users allowed to access CheckUser, ContextSwitching or Impersonnation plugins.
Also, an admin can not either check or use an anonymous identity in this case.
Append a rule to bypass identities use rule for specific users.