Fix a problem where second and later tabs in a window with a left-side tab bar that's limited by the 1/3 * content size bound will have fewer columns than it should. Issue 6371.

Store the preferred width of the left tab bar separately from its actual width, which is constrained by the width of the window. The preferred width is set by a manual drag and is persisted in user defaults. When the window is wide enough to accommodate the preferred width, the tab bar will grow up to but not beyond that size. Issue 5833

This reverts commit ed6754b1.

Add a menu item to the Toolbelt menu to save the current toolbelt's width as the default. Set the width from the pref the first time it is shown in a window.

Fix a bug where when the left-side tab bar or the toolbelt got resized smaller, only the current tab's splitview's width was adjusted. When that tab was closed, the other splitviews were larger and the window's size was based on them in fitWindowToTabs. This commit changes such drag operations to call fitTabsToWindow when dragging completes so all the splitviews will have the size size. See issue 4323.

Add a control to appearance prefs for whether to show tabs in fullscreen. Make the setting affect all windows rather than having a per-window setting.

Get rid of hold cmd to show tabs in fullscreen. Allow holding cmd to extend how long tabs are shown in fullscreen.

Fix bug where hodling cmd in fullscreen doesn't flash tabs if automatic tab flashing is turned off in prefs>appearance

Try to fix a crash where the iTermTabBarControlView's delegate is a dangling pointer because PseudoTerminal got released before iTermTabBarControlView. Not sure if this will work but it is cleaner, at least.