Decouple image shape matching from the `image` MediaType

The initial hard technical blocker:

new FieldPropExpression(EntityDataDefinition::create('media', 'image'), …)

needs to be able to be

new FieldPropExpression(EntityDataDefinition::create('media', ['image', 'acquia_dam_image']), …)

… but
\Drupal\Core\Entity\TypedData\EntityDataDefinition::create() does not allow that:

public static function create($entity_type_id = NULL, $bundle = NULL) {

Investigation led to discovering an upstream core issue for this: #2169813: Support deriving fields from entity definitions with multiple bundles → . Which … I happen to have contributed to 8 years ago for JSON:API. 😅👴

wim leers → credited bnjmnm → .

Tests are passing, and are proving that it is now possible to target different fields (i.e. bundle-specific fields) of the same field type across multiple bundles of the same entity type.

This effectively makes this behave similarly to how 📌 Pages have images usable for SEO purposes Active handled the picking of the the image to use in Metatags. (And this will automatically start happening on existing sites with this change.)

And … it actually works thanks to @bnjmnm's work on the Media Library Widget:

Future work

Note: the "same field type" requirement I referred to is simply because the props being targeted in each FieldPropExpression cannot (yet) vary by bundle; only the field name can. This could be expanded in a follow-up issue, which would allow for e.g. different media sources that all provide similar media: the Image MediaSource (powered by an image/file field type for local images), but a "remote image" MediaType — for example powered by core's OEmbed MediaSource, using the (disabled by default) Flickr oEmbed provider.

Created 📌 Support image shape matching from the `image` MediaSource: support both the `image` + `oembed` MediaSources simultaneously Active for that.

Tests are green! Follow-up for next steps exists.

Self-RTBC'ing and merging because nobody else knows the area well enough to review it.