Account for remapped faces in $COLUMNS and $LINES in Eshell

Account for remapped faces in $COLUMNS and $LINES in Eshell

* src/window.h (window_body_unit): New enum...
(window_body_width): ... use it.

* src/window.c (window_body_unit_from_symbol): New function.
(window_body_height, window_body_width): Make PIXELWISE a
'window_body_unit'.
(window-body-height, window-body-width): Accept 'remap' for PIXELWISE.
(window-lines-pixel-dimensions, window_change_record_windows)
(run_window_change_functions, resize_frame_windows, grow_mini_window)
(shrink_mini_window, scroll-left, scroll-right): Update calls to
'window_body_height' and 'window_body_width'.

* src/indent.c (compute_motion): Update calls to 'window_body_width'.

* lisp/eshell/em-ls.el (eshell-ls-find-column-widths)
(eshell-ls-find-column-lengths): Use 'window-body-width'.

* lisp/eshell/esh-var.el (eshell-variable-aliases-list): Use
'window-body-width' and 'window-body-height'.

* test/lisp/eshell/esh-var-tests.el (esh-var-test/window-height)
(esh-var-test/window-width): Rename to...
(esh-var-test/lines-var, esh-var-test/columns-var): ... and update
expected value.

* doc/lispref/windows.texi (Window Sizes): Document new behavior of
PIXELWISE argument for 'window-body-width' and 'window-body-height'.

* etc/NEWS: Announce this change (bug#55696).