/root: Install .cshrc and .profile links with the same mode.

Previously we would:

1. Install /root/.cshrc and /root/.profile with mode FILESMODE=644 as
requested in src/etc/root/Makefile and as echoed in
/etc/mtree/special.

2. Create hard links at /.cshrc and /.profile through CONFIGLINKS.

3. Because LINKSMODE was unset and defaults to NOBINMODE=444, change
the mode to 444.

This scenario is confusing, and mtree objects to it, which is bad for
warning fatigue in a security-relevant mechanism. (There are also
several other files mtree objects to out of the box -- we should fix
those too.)

With this change we install the links with the same mode as the
original files, in agreement with the mtree. The files, .cshrc and
.profile, are intended to be editable configuration files, so 644
makes sense while 444 makes no sense and gets in the way of editors
like vi.

Discussed on tech-userlevel:
https://mail-index.netbsd.org/tech-userlevel/2022/08/29/msg013498.html

XXX pullup-8
XXX pullup-9

branches: 1.4.24; 1.4.34;
We don't need to include <bsd.prog.mk> to install a few config files
just <bsd.files.mk> and <bsd.links.mk> is enough.

Noticed because <bsd.prog.mk> sets LINKSMODE to BINMODE and that does
the wrong thing at least for unprivileged builds.

branches: 1.3.6; 1.3.8; 1.3.12;
Move the emergancy terminfo database from /root to /rescue.

Install a minimal .terminfo and .terminfo.db in /root.
This allows terminfo to be used when /usr is not available.
Fixes PR misc/6879.

Consistently use CONFIGFILES & CONFIGLINKS (which enable the 'configinstall'
target) instead of using home-grown 'distribution' targets or using
FILES with the 'install' target.
Add some etc/ subdir Makefiles where appropriate.

XXX: some of etc/Makefile install-etc-files could be converted to CONFIGFILES.