replace "dep" with "go mod"

A simple "go mod init && go mod tidy && go mod vendor" was enough and
mostly seems to have picked the same revisions of the dependencies as
before. Notable exceptions are klog and gogo/protobuf.

vendor/k8s.io/apimachinery/pkg/api/meta/OWNERS

@@ -0,0 +1,27 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+reviewers:
+- thockin
+- smarterclayton
+- wojtek-t
+- deads2k
+- brendandburns
+- derekwaynecarr
+- caesarxuchao
+- mikedanese
+- liggitt
+- nikhiljindal
+- gmarek
+- janetkuo
+- ncdc
+- eparis
+- dims
+- krousey
+- markturansky
+- fabioy
+- resouer
+- david-mcmahon
+- mfojtik
+- jianhuiz
+- feihujiang
+- ghodss