Draft: messageTray: Remove expand on hover and simplify how notifications are dismissed

This simplifies the code of tracking hover and timeouts a lot, by removing the expand on hover and the special tracking of the hover state. We now have an expand button instead to allow users to expand the notification, which also fixed touch. This also reduces the timeout before a banner hides because now that we allow expanding in the notification drawer it's not as important anymore that the user clicks on buttons in the banner and they can have the same interaction later as well.

Relevant discussion: #7479 (comment 2133659) CC: @bertob @aday @fmuellner