revisit PRs touching on posinset, setsize, level

[pkra]

trafficstars

Following last week's discussion I spotted more work open PRs related to this. I tried to find all open pull requests:

• https://github.com/w3c/aria/pull/2341/
• https://github.com/w3c/aria/pull/2365
• https://github.com/w3c/aria/pull/2212#issuecomment-2547493548
• https://github.com/w3c/aria/pull/2170
• https://github.com/w3c/aria/pull/2104
• https://github.com/w3c/aria/pull/2091

It seems we might need to coordinate some of these