Finish hook attribute conversion of bigpipe and block modules

> I'm not sure how I feel about making it protected, it is technically api now, not sure why we want to restrict this further.

I think we similar discussions before.

Not every function is automatically an API, reducing API surface isn't a bad thing (for things that aren't useful). Making it protected/internal means it's easier to change and refactor it in the future.

There are no known calls (just one reference for someone doing something similar, it's just a way to share the code between the two hooks. It's exactly like what is done in #3502014: Clean up hook implementations in the Taxonomy module.

coding standards failed.

About the CR and things being removed without replacement, search for "There is no replacement". tons of deprecations like that, for example node_mark(), which has this CR: https://www.drupal.org/node/3514189

Personally, I'd not even bother with a CR and see if someone would prefer to have one. For me, with change records, it's always a question of value vs noise. There's not much useful that we could write except that you'd need to copy paste the code, which seems obvious, and the fact that there are no known usages on that. On the other side is the noise: dozens to hundreds of people will see some kind of notification, like a tweet, toot or whatever. But that's my personal opinion and the documentation page about that is still a bit vague.

I think this issue could use a title update, from the title it is not very clear what happened, I tried to change it so it's clearer.

The Needs Review Queue Bot tested this issue. It no longer applies to Drupal core. Therefore, this issue status is now "Needs work".

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