[Meta] Offer a revisions tab for all entities

Rerolled #21 and moved to an MR
Hiding patches

larowlan → changed the visibility of the branch 2452523-meta-offer-a to hidden.

Updating title to reflect this isn't a meta, there's code.

Will continue with tests tomorrow

Updated issue summary
This now includes tests and is ready for review
Testing on a client project its working nice 🙌

I just tested out the issue fork and it works like a charm - only found a problem with custom block content entities. The revision overview seems to work as expected (with the radio buttons to compare selected revisions), but when clicking Compare selected revisions, I get this error:

Drupal\Core\Entity\Exception\UndefinedLinkTemplateException: No link template 'revision' found for the 'block_content' entity type in Drupal\Core\Entity\EntityBase->toUrl() (line 211 of core/lib/Drupal/Core/Entity/EntityBase.php).

This looks great, thanks to everyone who worked on it.

@larowlan do you think we should add a test case for media revisions as well, so all core entity types with the generic revision UI are supported?

@hctom can you provide more info about your Drupal version and any other steps to reproduce it? The test coverage suggests that block content is working so perhaps you have a patch or custom/contrib module that is interfering?

Can do for media
I did have that issue with block content before one of the later pushes, so perhaps @hctom was testing an earlier version.
I fixed it whilst adding the tests.

I used the latest patch on a Drupal 10.3.6 install with nothing fancy in there. It's just a block content entity bundle with a custom bundle class.
I also updated the patch with the latest changes now, but the errors persists - and as far as I see, the tests do not show any problems, because they only test the revision overview currently and not the actual revision comparison, where this error occurres.

I was able to reproduce @hctom's results
Expanded the tests and fixed the issue

Back to needs review

Just checked the new changes by larowlan and I can confirm: comparing revisions of block content entities is now working as expected. Thank you!

Rebase is failing tests

Back to green, would be good to get another review on this