Hide/Show Caption and Alignment fields in for each entity embed

I tried this patch as I was looking for the same thing. The general idea works, but I have a couple suggestions.

One is the upgrade path if this is added when you already have a button. I had an existing button that was set to only allow the Teaser display mode and was showing the caption and alignment options. After adding the patch, all of those options went to blank, meaning all the display modes showed up as options and caption/alignment did not. I think this should maintain existing settings as the default: whatever I previously had in display mode, and caption/alignment on. Imagining this coming through as a release, some would be surprised to have the behaviour changed.

The second is that now the second page is unnecessary. The first page I select the entity I want to embed. The second page only shows me that same entity name again. Can that second page be skipped entirely if there are no options on it?

I was looking for a solution for this, and this patch looks like exactly what I was looking for.

@ryanrobinson_wlu For that to be skipped, we would need a separate patch for embed module itself, or alter the EntityEmbedDialog class from entity_embed, which we might want to avoid. The key is:

    if (!$form_state->get('step')) {
      // If an entity has been selected, then always skip to the embed options.
      if ($form_state->get('entity')) {
        $form_state->set('step', 'embed');
      }
      else {
        $form_state->set('step', 'select');
      }
    }

Where we want to skip the step if the form has no settings.

I've added an upgrade path.

For skipping the second step we would need to replicate the functionality of submitEmbedStep in submitAndShowEmbed in the case there are no settings, but we would miss the hook that is triggered there?

I'm not implementing this ATM because I don't need that, but just in case we want to do this in this same MR. Could be a follow-up or not implementing at all. I'd suggest a follow-up in any case, as this MR is useful as-is.

Added patch if it helps, but the MR should be the canonical source.