Set the 'field' property for Eshell output

Set the 'field' property for Eshell output

This makes Eshell work more like 'M-x shell', and lets the <home> key
move to the beginning of the user's input at the prompt (bug#60666).

* lisp/eshell/em-prompt.el (eshell-emit-prompt): Add 'field' property
to prompt.
(eshell-bol-ignoring-prompt): New function.

* lisp/eshell/esh-io.el: Declare 'eshell-interactive-print'...
(eshell-output-object-to-target): ... use it.

* lisp/eshell/esh-mode.el (eshell-output-filter-functions): Update
docstring.
(eshell-interactive-print): Set the output to have a field value of
'command-output'.
(eshell-output-filter): Rename to...
(eshell-interactive-filter): ... this, and take a buffer instead of a
process.

* lisp/eshell/esh-proc.el (eshell-interactive-process-filter): New
function, adapted from 'eshell-output-filter'...
(eshell-gather-process-output): ... use it.

* test/lisp/eshell/em-prompt-tests.el: New file.

* etc/NEWS: Announce this change.