Correctly parse X-Stream-Protocol-Version header

[tedyu]

What type of PR is this?
/kind bug

What this PR does / why we need it:
This PR iterates the components of X-Stream-Protocol-Version header and splits each by comma.
Non-empty protocol versions take part in negotiation.

Which issue(s) this PR fixes:
Fixes #89849

kube-apiserver: multiple comma-separated protocols in a single X-Stream-Protocol-Version header are now recognized, in addition to multiple headers, complying with RFC2616

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[tedyu]

/cc @liggitt

[liggitt]

I would suggest putting the []string -> []string transform into its own function, unit testing it, then just doing something like:

clientProtocols := commaSeparatedHeaderValues(req.Header[http.CanonicalHeaderKey(HeaderProtocolVersion)])

[tedyu]

@liggitt
PR has been updated with unit test

[tedyu]

/priority important-soon

[tedyu]

/test pull-kubernetes-e2e-gce

[k8s-ci-robot]

@tedyu: The following test failed, say /retest to rerun all failed tests:

Test name	Commit	Details	Rerun command
pull-kubernetes-node-e2e-containerd	8aada68	link	/test pull-kubernetes-node-e2e-containerd

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[liggitt]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liggitt, tedyu

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