The previous implementation in 6ae2b74ed2 only stopped at prompts,
which isn't the right behavior (bug#61545).
* lisp/eshell/em-prompt.el (eshell-forward-paragraph)
(eshell-backward-paragraph): Reimplement to handle prompts and
paragraphs (the latter by calling the original 'forward-paragraph').
* test/lisp/eshell/em-prompt-tests.el
(em-prompt-test/next-previous-prompt/multiline): Rename.
(em-prompt-test/forward-backward-paragraph-1): New function.
(em-prompt-test/forward-backward-paragraph)
(em-prompt-test/forward-backward-paragraph/multiline): New tests.