DEV: Admin webhooks interface issues (#19360)

1. The events table had broken styling, making each row overflow
2. It had confusing routes: `/:id` for "edit" and `/:id/events` for "show" (now it's `/:id/edit` and `/:id` respectively)
3. There previously was an unused backend action (`#edit`) - now it is used (and `web_hooks/:id/events` route has been removed)
4. There was outdated/misplaced/duplicated CSS
5. And more

app/controllers/admin/web_hooks_controller.rb

@@ -32,6 +32,10 @@ class Admin::WebHooksController < Admin::AdminController
     render_serialized(@web_hook, AdminWebHookSerializer, root: 'web_hook')
   end
 
+  def edit
+    render_serialized(@web_hook, AdminWebHookSerializer, root: 'web_hook')
+  end
+
   def create
     web_hook = WebHook.new(web_hook_params)
 
@@ -58,9 +62,6 @@ class Admin::WebHooksController < Admin::AdminController
     render json: success_json
   end
 
-  def new
-  end
-
   def list_events
     limit = 50
     offset = params[:offset].to_i