runtime: deprecate runc --criu / -criu-path option

runc option --criu is now ignored (with a warning), and the option will be
removed entirely in a future release. Users who need a non- standard criu
binary should rely on the standard way of looking up binaries in $PATH.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

runtime/v2/runc/options/next.pb.txt

@@ -58,6 +58,9 @@ file {
       number: 8
       label: LABEL_OPTIONAL
       type: TYPE_STRING
+      options {
+        deprecated: true
+      }
       json_name: "criuPath"
     }
     field {