Delete most of the boskos/ directory from kubernetes/test-infra

[ixdy]

Boskos has been moved to kubernetes-sigs/boskos and is mostly operational (pending #17718).

I think we're now ready to delete most of this subdirectory from test-infra.
I left behind the update_prow_config.sh script (though it should probabyl be moved somewhere else), along with the gcp_janitor.py script. For the latter, it'd be better to use the copy from kubernetes-sigs/boskos, but #17719 makes doing that tricky, and I don't really have the proper context to fix those legacy bootstrap janitor jobs.

This PR depends on #17721, so
/hold

[BenTheElder]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: BenTheElder, ixdy, stevekuznetsov

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[ixdy]

/hold cancel

[k8s-ci-robot]

@ixdy: Updated the job-config configmap in namespace default at cluster default using the following files:

• key test-infra-trusted.yaml using file config/jobs/kubernetes/test-infra/test-infra-trusted.yaml

In response to this:

Boskos has been moved to kubernetes-sigs/boskos and is mostly operational (pending #17718).

I think we're now ready to delete most of this subdirectory from test-infra.
I left behind the update_prow_config.sh script (though it should probabyl be moved somewhere else), along with the gcp_janitor.py script. For the latter, it'd be better to use the copy from kubernetes-sigs/boskos, but #17719 makes doing that tricky, and I don't really have the proper context to fix those legacy bootstrap janitor jobs.

This PR depends on #17721, so
/hold

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