cmd/k8s-operator: sprinkle debug logging throughout.

As is convention in the k8s world, use zap for structured logging. For
development, OPERATOR_LOGGING=dev switches to a more human-readable output
than JSON.

Updates #502

Signed-off-by: David Anderson <danderson@tailscale.com>

go.mod

@@ -24,6 +24,7 @@ require (
 	github.com/frankban/quicktest v1.14.0
 	github.com/fxamacker/cbor/v2 v2.4.0
 	github.com/go-json-experiment/json v0.0.0-20221017203807-c5ed296b8c92
+	github.com/go-logr/zapr v1.2.3
 	github.com/go-ole/go-ole v1.2.6
 	github.com/godbus/dbus/v5 v5.0.6
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da
@@ -64,6 +65,7 @@ require (
 	github.com/toqueteos/webbrowser v1.2.0
 	github.com/u-root/u-root v0.9.1-0.20221111022710-6e9699743f5d
 	github.com/vishvananda/netlink v1.1.1-0.20211118161826-650dca95af54
+	go.uber.org/zap v1.21.0
 	go4.org/mem v0.0.0-20210711025021-927187094b94
 	go4.org/netipx v0.0.0-20220725152314-7e7bdc8411bf
 	golang.org/x/crypto v0.3.0
@@ -154,7 +156,6 @@ require (
 	github.com/go-git/go-billy/v5 v5.3.1 // indirect
 	github.com/go-git/go-git/v5 v5.4.2 // indirect
 	github.com/go-logr/logr v1.2.3 // indirect
-	github.com/go-logr/zapr v1.2.3 // indirect
 	github.com/go-openapi/jsonpointer v0.19.5 // indirect
 	github.com/go-openapi/jsonreference v0.19.5 // indirect
 	github.com/go-openapi/swag v0.19.14 // indirect
@@ -297,7 +298,6 @@ require (
 	github.com/yeya24/promlinter v0.1.0 // indirect
 	go.uber.org/atomic v1.7.0 // indirect
 	go.uber.org/multierr v1.6.0 // indirect
-	go.uber.org/zap v1.21.0 // indirect
 	golang.org/x/exp/typeparams v0.0.0-20220328175248-053ad81199eb // indirect
 	golang.org/x/image v0.0.0-20201208152932-35266b937fa6 // indirect
 	golang.org/x/mod v0.6.0 // indirect