Change coverage map to treat hotspot_key as bytes rather than a PublicKeyBinary #72

Job	Run time
fmt	4s
clippy	1m 34s
build	4m 23s
tests (ingest)	1m 33s
tests (mobile-packet-verifier)	1m 37s
tests (file-store)	1m 26s
tests (reward-scheduler)	1m 2s
tests (task-manager)	46s
tests-postgres (boost-manager)	2m 8s
tests-postgres (iot-config)	2m 18s
tests-postgres (iot-packet-verifier)	3m 15s
tests-postgres (iot-verifier)	2m 9s
tests-postgres (mobile-config)	2m 3s
tests-postgres (mobile-verifier)	2m 4s
build-release	0s
	26m 22s

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