`nameFrom` can’t use `selector` fields

[Daaaaad]

Description

When a repeater uses a selector field as its nameFrom source, the row label shown in the back-office sidebar is JSON data.

'repeater' => [
  'name'     => 'Selected products',
  'nameFrom' => 'product',            // <— selector field
  'groups'   => [
    'product' => [
      'type'       => 'selector',
      'collection' => 'Product',
      'selector'   => '{id} - {name}',
    ],
  ],
],

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Steps to reproduce

1. Create a custom block with the configuration above.
2. In the BO page builder, add an item and pick a product via the selector.
3. Look at the repeater tree: the new row shows JSON data instead of the product label.

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Expected behavior

The row title should display the formatted string defined by the selector field
(e.g. 7 – Smoked Ardennes Ham).