Enable tokens on admin title field

tim_dj → changed the visibility of the branch 3285015-enable-tokens-on to hidden.

@basvredeling I've created a basic version of tokenizable admin titles. For now it only supports [paragraph:XXX] tokens
also I've added possibility to set a default admin title per paragraph type. So that we can for example add [paragraph:field_title_field] as default for certain types. If no admin title is set it will fallback to original summary.

@tim_dj I've changed the MR a bit and merged it into 4.x. Thanks.
I think we need 2 more things:

• A custom token that generates the paragraph summary as output. Just like is done inside the ParagraphBlocksLabeller:getTitle() when there is no admin title present. The \Drupal\paragraph_blocks\Entity\ParagraphBlocksEntity::getSummary() already does this, so that should be quite easy.
• Potentially, something like a drush command, to update all existing admin_titles, or just the ones that are empty, to a new tokenised structure.

Thanks @tim_dj, these changes have all been merged. I'll make a new 4.x release soon.

Part of release 4.0.0