Support embedded paragraphs

Patch for issue

1. +++ b/src/Plugin/EntityUsage/Track/ParagraphsEntityEmbed.php
   @@ -0,0 +1,63 @@
   +  public function parseEntitiesFromText($text) {
   +    $dom = Html::load($text);
   

   Before you do any parsing here you should check that embedded_paragraphs are in the target entity types.

2. +++ b/src/Plugin/EntityUsage/Track/ParagraphsEntityEmbed.php
   @@ -0,0 +1,63 @@
   +      $embeddedPara = $this->entityTypeManager
   +        ->getStorage('embedded_paragraphs')
   +        ->loadByProperties(['uuid' => $node->getAttribute('data-paragraph-id')]);
   +      if (empty($embeddedPara)) {
   +        return [];
   +      }
   +      /** @var \Drupal\paragraphs_entity_embed\Entity\EmbeddedParagraphs $embeddedPara */
   +      $embeddedPara = reset($embeddedPara);
   +      $para = $embeddedPara->getParagraph();
   +      if (empty($para)) {
   +        return [];
   +      }
   

   It'd be great if we can do this without loading entities. Perhaps we can use an aggregate entity query here to get the embedded paragraph ID. For an example aggregate query see \Drupal\content_moderation\ModeratedNodeListBuilder::getEntityRevisionIds

3. +++ b/src/Plugin/EntityUsage/Track/ParagraphsEntityEmbed.php
   @@ -0,0 +1,63 @@
   +      // Add tracking for internal paragraph target being used by the embedded paragraph.
   +      $this->usageService->registerUsage($para->id(), 'paragraph', $embeddedPara->getId(), 'embedded_paragraphs', $embeddedPara->language()->getId(), $embeddedPara->getRevisionId(), $this->pluginId, 'paragraph_target_id');
   

   Here we need to check if embedded_paragraphs are in the source types I think

Here's a version that solves these concerns:

1. & 3. - The tracker now checks that embedded_paragraphs can be used as sources and that paragraphs can be targets. If not true, no tracking occurs and a logger message is output once per instance.

In addition, the settings form now has a validation that will not let this tracker be selected unless emebedded_paras is an allowed source and paras are an allowed target. Message also suggests they should be target/sources too.

Also, the tracker plugin is disabled unless the paragraphs_entity_embed provider module is enabled. (provider annotation)

2. - The required info is retrieved via 2 queries now instead of loading entities.

Changing title to reflect that the attached patch also improves tracking paragraphs back to the 'linkable' source (e.g. node, etc.) and not just the parent item. This is independent of if embedded paragraphs are used.

Thank you for filing this and for contributing.
I am very reluctant to add more code and special-cases to the list controller, which is already somewhat messy code special-casing paragraphs and blocks.
I'd rather we can wait until ✨ Issue Event for Row Rendering Active lands, then other modules can alter the list in any way they want.
Along these lines, I also believe the new plugin and settings form validation code should be part of the "Paragraphs entity embed" contrib module, how about we move this ticket into their issue queue?