Improve evaluation of conditional Eshell forms

Improve evaluation of conditional Eshell forms

This simplifies the logic for building these forms and also fixes an
issue where a subcommand in a "&&" or "||" conditional had its output
suppressed.

* lisp/eshell/esh-cmd.el (eshell-structure-basic-command): Make
obsolete.
(eshell-silence-test-command): New function...
(eshell-rewrite-while-command, eshell-rewrite-if-command): ... use it,
and make the command form ourselves.
(eshell-parse-pipeline): Use 'and' and 'or' to make the conditional
command sequence.
(eshell-command-success): New macro.
(eshell-do-eval): Add support for 'and' and 'or' forms.

* test/lisp/eshell/esh-cmd-tests.el (esh-cmd-test/and-operator/output)
(esh-cmd-test/or-operator/output): New tests.

(cherry picked from commit 673c906a5b7255987c09f534de45e555fc7fc9ae)