Refactor of Varnish image purge and reduce the number of requests

I've cleaned-up the change created by Jose Jiménez in https://git.drupalcode.org/project/varnish_purge/-/merge_requests/8.

The summary of the overall change in MR!10:
1. The purging of entity images is queued instead of performing the purging requests from within the entity_update hook.
2. The purging logic is moved from entity_update hook into purge module plugins.

The summary of the interdiff of MR!8 and MR!10 is the following:
1. The configuration form moved to the varnish_image queuer plugin.
2. The patch file which was commited in MR!8 is removed.

Thanks for the contribution, would it be possible if you could update the patch against the latest 8.x-2.x-dev?

Created a patch file based on maijs his MR

Something didn't copy well, updated the patch.