policy: Add optional `boringssl` support #2400

Job	Run time
cleanup	4s
changed-multicluster	16s
tag	5s
changed-viz	16s
changed-policy	12s
build-cli	4m 46s
build-core (cni-plugin)	2m 3s
build-core (controller)	1m 54s
build-core (policy-controller)	10m 38s
build-core (proxy)	2m 18s
build-ext (jaeger-webhook)	1m 40s
build-ext (metrics-api)	1m 41s
build-ext (tap)	1m 42s
build-ext (web)	6m 5s
test-core (cni-calico-deep)	5m 42s
test-core (deep)	5m 9s
test-ext (cluster-domain)	5m 42s
test-ext (default-policy-deny)	5m 43s
test-ext (external)	6m 55s
test-ext (rsa-ca)	3m 17s
test-ext (helm-upgrade)	6m 21s
test-ext (uninstall)	5m 47s
test-ext (upgrade-edge)	6m 28s
test-ext (upgrade-stable)	7m 8s
test-policy (v1.21)	9m 30s
test-policy (v1.26)	9m 13s
test-viz	0s
test-multicluster	0s
	1h 50m 35s

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