[6.x] Adjust listing skeleton to match configured features

[daun]

This makes the skeleton UI of listings check for configured features. The search bar skeleton is only shown when search is enabled; the column customization button skeleton is only shown if columns can be customized; etc.

Example

Using the Listing component with no filters and presets and columns disabled.

<Listing
  ref="listing"
  :url="endpoint"
  :columns="columns"
  :allow-presets="false"
  :allow-customizing-columns="false"
>

Before

After