Don't skip empty lines when fitting mini frame to buffer (Bug#44080)

Don't skip empty lines when fitting mini frame to buffer (Bug#44080)

* lisp/window.el (fit-mini-frame-to-buffer,
window--resize-mini-frame, fit-frame-to-buffer,
fit-frame-to-buffer-1): By default, fit a mini frame without skipping its
buffer's leading or trailing empty lines.
* src/frame.c (resize-mini-frames): Update doc-string.
* lisp/cus-start.el (resize-mini-frames): Update for customize.
* doc/lispref/minibuf.texi (resize-mini-frames): Update description.