Add `coverage_map` crate to provide `CoverageMapBuilder` and `CoverageMap` data structures #46

Job	Run time
build	1m 56s
clippy	1m 32s
fmt	4s
tests (ingest)	1m 29s
tests (mobile-packet-verifier)	1m 21s
tests (file-store)	1m 18s
tests (reward-scheduler)	41s
tests (task-manager)	57s
tests-postgres (boost-manager)	2m 9s
tests-postgres (iot-config)	2m 19s
tests-postgres (iot-packet-verifier)	3m 14s
tests-postgres (iot-verifier)	2m 13s
tests-postgres (mobile-config)	2m 14s
tests-postgres (mobile-verifier)	2m 24s
build-release	0s
	23m 51s

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