Updated empty state for Attributes

[mattsherman]

Before

Empty state when no global attributes exist:

Empty state when global attributes exist:

After (Design)

Empty state whenever no attributes are assigned to a product:

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Acceptance criteria

• We no longer check if any global attributes exist in the store. The empty state with the new attribute form is always shown when no attributes are added to the product (custom or global).
• The empty state with the attribute creation form replaces the empty state with the badge icon.
• The list has the same controls implemented in [Enhancement]: Add new empty state shown when no attributes #37151 (with the Add new and Add existing buttons).
• If an existing (global) attribute is added when only an empty attribute create form is showing (no other attributes on product), the empty attribute create form is removed