After react 18 update, the tab node may not yet be rendered
by tabBar.jsx when we try to scroll it into view in Zotero_Tabs.select.
- To make sure scrolling happens when rendering is done, move scroll-related
logic into a useEffect of tabBar.jxs. It also makes sure that we'll scroll to
a selected tab if it is moved via context menu to the very beginning or the end.
- Added a small scroll-padding to tabs container to make sure the border
does not get cutoff after the tab is scrolled into view instead of
JS code accounting for the border.
- Fixed a glitch where the pinned library tab would not get selected
on shift-tab from opened tabs menu.
Fixes: #4382
e6b5ba60dd