pane: Add settings to hide the tab bar buttons (#23752)

This PR adds the `show_tab_bar_buttons` under `tab_bar` that allows
hiding the "New", "Split Pane", and "Zoom" buttons to the left of the
pane tab bar.

Release Notes:

- Added a new `show_tab_bar_buttons` setting, under `tab_bar`, that
enables hiding the pane tab bar buttons.