feat: Add support for search_conversations in copilot (#11520)

Earlier, we were manually checking if a user was an agent and filtering
their conversations based on inboxes. This logic should have been part
of the conversation permissions service.

This PR moves the check to the right place and updates the logic
accordingly.

Other updates:
- Add support for search_conversations service for copilot.
- Use PermissionFilterService in contacts/conversations, conversations,
copilot search_conversations.

---------

Co-authored-by: Sojan <sojan@pepalo.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Muhsin Keloth <muhsinkeramam@gmail.com>

app/finders/conversation_finder.rb

@@ -88,7 +88,10 @@ class ConversationFinder
 
   def find_conversation_by_inbox
     @conversations = current_account.conversations
-    @conversations = @conversations.where(inbox_id: @inbox_ids) unless params[:inbox_id].blank? && @is_admin
+
+    return unless params[:inbox_id]
+
+    @conversations = @conversations.where(inbox_id: @inbox_ids)
   end
 
   def find_all_conversations