patch 9.0.1726: incorrect heights in win_size_restore()

patch 9.0.1726: incorrect heights in win_size_restore()

Problem: incorrect heights in win_size_restore()
Solution: avoid restoring incorrect heights in win_size_restore()

Changing 'showtabline' or 'cmdheight' in the cmdwin restores incorrect
window heights after closing the cmdwin.

This may produce a gap between the cmdline and the window above.

Solution: restore window sizes only if the number of lines available for windows
changed; subtract the rows of the tabline, cmdline and last window's statusline
from 'lines' (other statuslines don't matter).

closes: #12704

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