Support multiple implementations for hook_field_widget_third_party_settings_form

Problem/Motivation

Since the flood gates are open for multiple implementations of the same hook in the same modules, the hook field_widget_third_party_settings_form doesn't support that since it expects each module to have only one implementation

Steps to reproduce

Use the Hook attribute twice in the same module

#[Hook('field_widget_third_party_settings_form')]                                                                                                                                                             
  public function fieldWidgetThirdPartySettingsForm(WidgetInterface $plugin, FieldDefinitionInterface $field_definition, $form_mode, $form, FormStateInterface $form_state) {

adding different form elements.

Proposed resolution

Merge all elements of the same module in the same form array

Remaining tasks

Code solutions
Add tests

User interface changes

None