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/apis/meta/v1/OWNERS

@@ -0,0 +1,33 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+reviewers:
+- thockin
+- smarterclayton
+- wojtek-t
+- deads2k
+- brendandburns
+- caesarxuchao
+- liggitt
+- nikhiljindal
+- gmarek
+- erictune
+- davidopp
+- sttts
+- quinton-hoole
+- luxas
+- janetkuo
+- justinsb
+- ncdc
+- soltysh
+- dims
+- madhusudancs
+- hongchaodeng
+- krousey
+- mml
+- mbohlool
+- david-mcmahon
+- therc
+- mqliang
+- kevin-wangzefeng
+- jianhuiz
+- feihujiang