lib: add `register_buffers_*` family of functions

[fathyb]

This introduces:

• Submitter::register_buffers_tags corresponding to io_uring_register_buffers_tags
• Submitter::register_buffers_sparse corresponding to io_uring_register_buffers_sparse
• Submitter::register_buffers_update_tag corresponding to io_uring_register_buffers_update_tag

[quininer]

Would you be willing to add relevant docs and tests?

[fathyb]

Yes, I should push that today. I opened the PR as a draft to let others pick it in case they were looking for it. I should've filled the description, apologies for that!

[quininer]

Are you willing to resolve this conflict?

[saiintbrisson]

@quininer can close this one