Add `Delete` button to label edit view

What does this MR do and why?

Related to #345195 (closed)

Adds a Delete button to the label edit view. This change affects Project, Group, and Admin label management.

Screenshots or screen recordings

Admin labels

Desktop

Before	After

Mobile

Before	After

Project labels

Desktop

Before	After

Mobile

Before	After

Group labels

Desktop

Before	After

Mobile

Before	After

How to set up and validate locally

Admin labels

1. Navigate to /admin/labels
2. Create a label
3. Edit the label

Project labels

1. Navigate to a project -> Project information -> Labels
2. Create a label
3. Edit the label

Group labels

1. Navigate to a group -> Group information -> Labels
2. Create a label
3. Edit the label

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

app/models/label.rb

@@ -260,7 +260,7 @@ def hook_attrs
     attributes
   end
 
-  def present(attributes)
+  def present(attributes = {})
     super(**attributes.merge(presenter_class: ::LabelPresenter))
   end