StaticPropSource::parse() could validate prop value keys

Overview

In 📌 Split model values into resolved and raw Active we discovered that we have tests that store garbage data in prop values, and this was not detected:

    $static_image_prop_source = [
      'sourceType' => 'static:field_item:entity_reference',
      'value' => [
        'alt' => 'This is a random image.',
        'width' => 100,
        'height' => 100,
        'target_id' => 3,
      ],

Only target_id is actually required here.

StaticPropSource::parse() could assert that only the required keys are in the array, alerting developers to the fact unused data is present.

Proposed resolution

User interface changes