Don't create config while syncing

Problem/Motivation

Importing a new registration type lead to error:

    The import failed due to the following reasons:
    Deleted and replaced configuration entity "core.entity_view_display.registration.online.summary"

Steps to reproduce

Install commerce registration on dev and prod.
Create a registration type on dev.
Export config on dev.
Import config into prod.

Proposed resolution

Don't create summary view mode while importing config, expect config to be complete.

The cause is this code:

function commerce_registration_entity_insert(EntityInterface $entity) {
  if ($entity instanceof RegistrationTypeInterface) {
    if (EntityViewMode::load('registration.summary')) {
      // Create a summary view for new registration types.
      $display = EntityViewDisplay::create([

Use \Drupal::service('config.installer')->isSyncing() to avoid creating config while syncing.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.