Add `coverage_map` crate to provide `CoverageMapBuilder` and `CoverageMap` data structures #68

Job	Run time
clippy	1m 37s
fmt	7s
build	1m 56s
tests (mobile-packet-verifier)	1m 37s
tests (file-store)	1m 37s
tests (ingest)	1m 30s
tests (reward-scheduler)	43s
tests (task-manager)	42s
tests-postgres (boost-manager)	2m 17s
tests-postgres (iot-config)	2m 38s
tests-postgres (iot-packet-verifier)	3m 21s
tests-postgres (iot-verifier)	2m 12s
tests-postgres (mobile-config)	2m 24s
tests-postgres (mobile-verifier)	2m 32s
build-release	0s
	25m 13s

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