Previously it might've reused a shared state.

Deals with https://github.com/zed-industries/community/issues/2262 also
fixes influencer's feedback.

No gpui2 port, due to 0 scrollable functionality in it yet.

Release Notes:

- Fixed tabs not being scrolled to on buffer (re)open
(https://github.com/zed-industries/community/issues/2262)