Add `coverage_map` crate to provide `CoverageMapBuilder` and `CoverageMap` data structures #43

Job	Run time
build	4m 32s
clippy	1m 34s
fmt	7s
tests (ingest)	1m 51s
tests (file-store)	1m 43s
tests (mobile-packet-verifier)	1m 23s
tests (reward-scheduler)	36s
tests (task-manager)	46s
tests-postgres (boost-manager)	2m 6s
tests-postgres (iot-config)	2m 31s
tests-postgres (iot-packet-verifier)	2m 35s
tests-postgres (iot-verifier)	2m 24s
tests-postgres (mobile-config)	2m 15s
tests-postgres (mobile-verifier)	31s
build-release	0s
	24m 54s

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