Mannequin name improvements for 1.21.9->1.21.7

[roccodev]

This slightly changes the way mannequin names are handled:

• When spawning the second entity, the new name from the profile is now used to name the player info entry. This is nice because it allows registering the mannequin in scoreboard teams.
• Team registration is only performed when the second entity is spawned, this is because the mannequin's name can change in-between due to the above. Perhaps I could also add a way to disable this, because in some cases (I'd imagine on track/untrack) it may override the team set by the server/plugins?
• When the mannequin has no CustomName, its nametag is hidden (by setting the option in its team), which matches 1.21.9+ behavior. Technically in 1.21.9 this depends on CustomNameVisible (otherwise the name can display but only on hover), not sure whether I should change it to match that, because in 1.8 and 1.9 the name is either always displayed or always hidden.