Skaffold should output which kube-context + cluster is being used

It should be more clear for users (and people trying to offer support by looking at logs!) which kube-context and cluster is being used.
```
$ skaffold dev
Listing files to watch...
- skaffold-example
Generating tags...
- skaffold-example -> skaffold-example:v1.34.0-60-gef8185519
Checking cache...
- skaffold-example: Not found. Building
Starting build...
Building [skaffold-example]...
```

This information is shown with `-vinfo`, but most users do not run at this level:
```
$ skaffold dev -v info
INFO[0000] Skaffold &{Version:v1.34.0-60-gef8185519 ConfigVersion:skaffold/v2beta26 GitVersion: GitCommit:ef818551948c82de81ef4308aef7dbcb36d3dede BuildDate:2021-11-15T15:47:08Z GoVersion:go1.17.2 Compiler:gc Platform:darwin/arm64 User:} subtask=-1 task=DevLoop
INFO[0000] Loaded Skaffold defaults from "/Users/bdealwis/.skaffold/config" subtask=-1 task=DevLoop
INFO[0000] Using kubectl context: gke_k8s-skaffold_us-west1_test-cluster subtask=-1 task=DevLoop
INFO[0001] build concurrency first set to 1 parsed from *local.Builder[0] subtask=-1 task=DevLoop
```