Implements server-side apply

[seans3]

• Implements server-side apply
• Adds --server-side to kpt live apply to turn on the server-side apply
• Adds --force-conflicts bool for overwriting applied fields if field manage conflict.
• Adds --field-manager string flag to dynamically determine the applied fields "owner".
• Adds a server-side apply e2e test
• Also Manually tested with all three flags.

$ kapply apply --server-side ~/testdata/testdata-namespace-1
namespace/test-namespace serversideapplied
pod/pod-a serversideapplied
pod/pod-b serversideapplied
pod/pod-c serversideapplied
4 resource(s) applied. 0 created, 0 unchanged, 0 configured, 4 serverside applied
0 resource(s) pruned, 0 skipped

$ kubectl get po -n test-namespace
NAME    READY   STATUS    RESTARTS   AGE
pod-a   1/1     Running   0          11s
pod-b   1/1     Running   0          11s
pod-c   1/1     Running   0          11s

$ kubectl get cm -n test-namespace
NAME                 DATA   AGE
inventory-40650014   4      11s

$ kapply apply --server-side ~/testdata/testdata-namespace-2
pod/pod-b serversideapplied
pod/pod-c serversideapplied
pod/pod-d serversideapplied
3 resource(s) applied. 0 created, 0 unchanged, 0 configured, 3 serverside applied
pod/pod-a pruned
namespace/test-namespace prune skipped
1 resource(s) pruned, 1 skipped

$ kubectl get po -n test-namespace
NAME    READY   STATUS    RESTARTS   AGE
pod-b   1/1     Running   0          29s
pod-c   1/1     Running   0          29s
pod-d   1/1     Running   0          14s

$ kubectl get cm -n test-namespace
NAME                 DATA   AGE
inventory-40650014   3      29s

[mortent]

This looks good so far. For force-conflicts I think we should just use the same approach as kubectl unless we have a good reason to do something different.

[seans3]

/assign @mortent

[mortent]

/lgtm

[k8s-ci-robot]

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