PERF: Reduce DB queries when serializing ignore/mute information (#8629)

* PERF: Cache ignored and muted user ids in the current_user object
* PERF: Avoid DB queries when checking ignore/mute permission in guardian

lib/guardian.rb

@@ -463,10 +463,10 @@ class Guardian
     UserExport.where(user_id: @user.id, created_at: (Time.zone.now.beginning_of_day..Time.zone.now.end_of_day)).count == 0
   end
 
-  def can_mute_user?(user_id)
+  def can_mute_user?(target_user)
     can_mute_users? &&
-      @user.id != user_id &&
-      User.where(id: user_id, admin: false, moderator: false).exists?
+      @user.id != target_user.id &&
+      !target_user.staff?
   end
 
   def can_mute_users?
@@ -474,8 +474,8 @@ class Guardian
     @user.staff? || @user.trust_level >= TrustLevel.levels[:basic]
   end
 
-  def can_ignore_user?(user_id)
-    can_ignore_users? && @user.id != user_id && User.where(id: user_id, admin: false, moderator: false).exists?
+  def can_ignore_user?(target_user)
+    can_ignore_users? && @user.id != target_user.id && !target_user.staff?
   end
 
   def can_ignore_users?