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/client-go/tools/cache/OWNERS

@@ -0,0 +1,51 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+approvers:
+- thockin
+- lavalamp
+- smarterclayton
+- wojtek-t
+- deads2k
+- caesarxuchao
+- liggitt
+- ncdc
+reviewers:
+- thockin
+- lavalamp
+- smarterclayton
+- wojtek-t
+- deads2k
+- brendandburns
+- derekwaynecarr
+- caesarxuchao
+- mikedanese
+- liggitt
+- nikhiljindal
+- erictune
+- davidopp
+- pmorie
+- janetkuo
+- justinsb
+- eparis
+- soltysh
+- jsafrane
+- dims
+- madhusudancs
+- hongchaodeng
+- krousey
+- markturansky
+- fgrzadkowski
+- xiang90
+- mml
+- ingvagabund
+- resouer
+- jessfraz
+- david-mcmahon
+- mfojtik
+- '249043822'
+- lixiaobing10051267
+- ddysher
+- mqliang
+- feihujiang
+- sdminonne
+- ncdc