Update c/image to v4.0.1 and buildah to 1.11.3

This requires updating all import paths throughout, and a matching
buildah update to interoperate.

I can't figure out the reason for go.mod tracking
	github.com/containers/image v3.0.2+incompatible // indirect
((go mod graph) lists it as a direct dependency of libpod, but
(go list -json -m all) lists it as an indirect dependency),
but at least looking at the vendor subdirectory, it doesn't seem
to be actually used in the built binaries.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/containers/libtrust/CONTRIBUTING.md

@@ -0,0 +1,13 @@
+# Contributing to libtrust
+
+Want to hack on libtrust? Awesome! Here are instructions to get you
+started.
+
+libtrust is a part of the [Docker](https://www.docker.com) project, and follows
+the same rules and principles. If you're already familiar with the way
+Docker does things, you'll feel right at home.
+
+Otherwise, go read
+[Docker's contributions guidelines](https://github.com/docker/docker/blob/master/CONTRIBUTING.md).
+
+Happy hacking!