devel/autoconf*: restructure to prepare for 2.71

• Rename autoconf 2.13 port directory, package, and command all to autoconf2.13 just like ports like perl and python.
• Let USES=autoreconf run gtkdocize if necessary.
• Rewrite autoconf-wrapper and rename it autoconf-switch to reflect better what it does.
• Delete patch-bison. It has been reverted upstream.
• Add a patch to let autoreconf set the AUTOCONF environment variable so subprocesses like automake use the correct version.
• Make building of info files optional.
• Address portlint, portclippy, portfmt issues in devel/autoconf*.

PR: 259556, 263970