Update github.com/opencontainers/runtime-tools to v0.6.0

Also add new dependencies on github.com/xeipuuv/gojson* (brought up by
new runtime-tools) and adapt the containerd/cri code to replace the APIs
that were removed by runtime-tools.

In particular, add new helpers to handle the capabilities, since
runtime-tools now split them into separate sets of functions for each
capability set.

Replace g.Spec() with g.Config since g.Spec() has been deprecated in the
runtime-tools API.

Signed-off-by: Filipe Brandenburger <filbranden@google.com>

vendor/github.com/opencontainers/runtime-tools/filepath/doc.go

@@ -0,0 +1,6 @@
+// Package filepath implements Go's filepath package with explicit
+// operating systems (and for some functions and explicit working
+// directory).  This allows tools built for one OS to operate on paths
+// targeting another OS.  For example, a Linux build can determine
+// whether a path is absolute on Linux or on Windows.
+package filepath