patch 9.1.0169: current window number returned by tabpagewinnr may be outdated

patch 9.1.0169: current window number returned by tabpagewinnr may be outdated

Problem:  current window number returned by tabpagewinnr may be outdated
          when called from win_execute for the original tabpage.
Solution: update the original tabpage's tp_curwin in switch_win; use
          {un}use_tabpage instead. Don't do it in restore_win to ensure
          tp_curwin of the temporarily visited tabpage is unchanged from
          switch_win visiting it, as before. (Sean Dewar)

Maybe restore_win should only restore tp_curwin if
`curtab == switchwin->sw_curtab`, in case the user changed tabpages from within
win_execute, but not doing that is consistent with the old behaviour.

related: #14186

Signed-off-by: Sean Dewar <6256228+seandewar@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>