Default value bug for same name fields

Problem/Motivation

When we have two shs fields with the same name - one attached to the node and another attached to a paragraph we get the same default value in shs field in the paragraph as the one in the node.

Steps to reproduce

1. Create a shs field and attache it to a node type.
2. Create a paragraph type and attach to it a shs field with the same name as the one attached to the node.
3. Create a paragraph field in the node from the newly created paragraph type.

Proposed resolution

the code in src/Plugin/Field/FieldWidget/OptionsShsWidget.php:

  $field_name = $this->fieldDefinition->getName();
    $default_value = $element['#default_value'] ?: NULL;
    $user_input = $form_state->getUserInput();
    if (isset($user_input[$field_name])) {
      $default_value = $user_input[$field_name];
    }

needs to be adapted so element parents are taken into account

API changes

Data model changes