Add script to write prow branchprotector checks contexts

[BobyMCbobs]

given output of ./hack/list-checks.sh (in this branch or #204), generate or update configuration consumable in Prow's branchprotector (https://docs.prow.k8s.io/docs/components/optional/branchprotector)

branch based off of #204

usage

dump the state of the world

./hack/list-checks.sh | ./hack/set-bp-yaml-checks.sh PATH_TO_CONFIG.yaml sow

input the latest workflow contexts

./hack/list-checks.sh | ./hack/set-bp-yaml-checks.sh PATH_TO_CONFIG.yaml update

applying with a container image

podman run -it --rm \
  -v "PATH_TO_TOKEN:PATH_TO_TOKEN:row" \
  -v "PATH_TO_CONFIG:PATH_TO_CONFIG:ro" \
  gcr.io/k8s-prow/branchprotector:v20231011-acf4a2e26b \
    --github-token-path PATH_TO_TOKEN \
    --config-path PATH_TO_CONFIG.yaml # --confirm

or applying with go run

go run k8s.io/test-infra/prow/cmd/branchprotector@acf4a2e26b --github-token-path PATH_TO_TOKEN --config-path PATH_TO_CONFIG.yaml # --confirm

[BobyMCbobs]

@quiffman, thank you!