Switch to fully statically linked binaries and use scratch as a base
image.
Switching to the virtually empty scratch base image means that the
default/minimal NFD image only supports running hooks that are truly
statically linked (e.g. normal go binaries that are "almost" statically
linked stop working). The documentation has been already stating this
(i.e. that only statically-linked binaries are supported) - i.e. we have
had no promise of supporting other than that. Also, hooks are now
deprecated and even disabled by default so the possibility of real user
impact should be small.
Make distroless/base as the base image for the default image,
effectively making the minimal image as the default. Add a new "full"
image variant that corresponds the previous default image. The
"*-minimal" container image tag is provided for backwards compatibility.
The practical user impact of this change is that hook support is limited
to statically linked ELF binaries. Bash or Perl scripts are not
supported by the default image, anymore, but the new "full" image
variant can be used for backwards compatibility.
Introduce two main sections "Deployment" and "Usage" and move "Developer
guide" to the top level, too. In particular, split the huge
deployment-and-usage file into multiple parts under the new main
sections. Move customization guide from "Advanced" to "Usage".
This patch also renames "Advanced" to "Reference" as only that is left
there is reference documentation.
