Generate register functions for APIs

[damemi]

This updates api/hack/update-codegen.sh to call gen_register, which generates register code for our APIs. This also fixes broken code for calls to Resource()

[damemi]

Need to check this, might be a mistake

[damemi]

Going to hold on merging this, there are a bunch of weird warnings when generating the clients such as:

$ make generate-client
GOWORK=off go mod vendor
./hack/update-codegen.sh
Generating register code for 2 targets
W1218 15:42:34.862642   72290 parse.go:817] Making unsupported type entry "any" for: &types.Alias{obj:(*types.TypeName)(0x14000132b90), orig:(*types.Alias)(0x140001120c0), tparams:(*types.TypeParamList)(nil), targs:(*types.TypeList)(nil), fromRHS:(*types.Interface)(0x14000132af0), actual:(*types.Interface)(0x14000132af0)}
W1218 15:42:34.863196   72290 parse.go:817] Making unsupported type entry "reflect.uncommonType" for: &types.Alias{obj:(*types.TypeName)(0x14001eca500), orig:(*types.Alias)(0x140012e9100), tparams:(*types.TypeParamList)(nil), targs:(*types.TypeList)(nil), fromRHS:(*types.Named)(0x1400082ed20), actual:(*types.Named)(0x1400082ed20)}

which seems to be an actual issue due to kubernetes/gengo#281. Unfortunately, the version of k8s.io/code-generator that pulls in the gengo fix is also currently broken due to kubernetes/kubernetes#129290 (caused by a different change in gengo)