Get SDC components inserting

Problem/Motivation

The Component plugin in embedded_content_sdc has two bugs
that prevent SDC components from working when embedded via CKEditor:

1. build() returns an empty array — When a user embeds
   an SDC component in CKEditor and saves the node, nothing is rendered on the frontend.
   The build() method returns [] instead of a render array that
   uses Drupal's #type => 'component' element to render the SDC component
   with its saved props and slots.
2. buildConfigurationForm() crashes with a TypeError —
   The method calls buildForm() twice: once via
   cl_editorial_component_mappings_form() and again directly via
   ComponentInputToForm::buildForm(). The second call passes
   $form_state->getValues() as the current input, which is an empty array on
   initial form load. This causes the schema-forms library to throw:
   "Adaptor SchemaForms\Drupal\FormGeneratorDrupal received invalid input data:
   []". The error appears in the CKEditor dialog as: "The subform and parent form
   must contain the #parents property".

Steps to reproduce

1. Enable embedded_content_sdc and configure an Embedded Content button
   for a CKEditor text format.
2. Create an SDC component in a custom module (e.g., a component with string
   props).
3. Edit a node, click the Embedded Content button in CKEditor, and select your SDC
   component from the dropdown.
4. Observed: An error message appears in the dialog, and if the
   form does render, saving the node produces no visible output for the component.
5. Expected: The component's configuration form renders in the
   dialog, and the component renders on the frontend after saving.

Proposed resolution

MR !4 fixes both issues in Component.php:

• build(): Renders the SDC component using Drupal's
  #type => 'component' render element, passing #props and
  #slots from $this->configuration.
• buildConfigurationForm(): Replaces the broken
  double buildForm() call with a single call to
  cl_editorial_component_mappings_form(), passing
  $this->configuration instead of $form_state->getValues().
  This also removes the now-unused ComponentInputToForm import.

Remaining tasks

• Review and merge MR !4.

User interface changes

None.

API changes

None.

Data model changes

None.