Fix handling of Eshell debug modes

Fix handling of Eshell debug modes

Previously, these were enabled/disabled at byte-compilation time, but
we want to control them at runtime.

* lisp/eshell/esh-cmd.el (eshell-eval-command): Call
'eshell-debug-command-start'.
(eshell-manipulate): Check 'eshell-debug-command' at runtime.  Update
callers.
(eshell-debug-command): Move to "esh-util.el".
(eshell/eshell-debug, pcomplate/eshell-mode/eshell-debug): Move to
"em-basic.el".
(eshell-debug-show-parsed-args): Update implementation.

* lisp/eshell/esh-util.el (eshell-debug-command): Move from
"esh-cmd.el" and convert to a list.
(eshell-debug-command-buffer): New variable.
(eshell-condition-case): Check 'eshell-handle-errors' at runtime.
(eshell-debug-command-start): New function.
(eshell-debug-command): Move from "esh-cmd.el" and convert to a macro.

* lisp/eshell/em-basic.el (eshell/eshell-debug)
(pcomplete/eshell-mode/eshell-debug): Move from "esh-cmd.el" and
reimplement.

* lisp/eshell/eshell.el (eshell-command): Pass the original input to
'eshell-eval-command'.

* doc/misc/eshell.texi (Built-ins): Update documentation for
'eshell-debug'.