Customer Search: Empty state for non-results searches

[iamgabrielma]

From review: #7880 (review)

• There's no empty state yet, just a blank white screen.

The existing OrderCustomerListView is a SwiftUI wrapper for SearchViewController, and the latter already has an implementation for this case using displayEmptyState()

Also consider cleaning search results each time we start a new search, or leave them as they are.