coverage: count number of executions per line #1984

Job	Run time
Build Echidna on ubuntu-20.04	5m 38s
Build Echidna on macos-13	5m 33s
Build Echidna on windows-latest	15m 28s
Test with solc 0.4.25 on ubuntu-latest	4m 57s
Test with solc 0.5.7 on ubuntu-latest	3m 34s
Test with solc 0.6.12 on ubuntu-latest	3m 43s
Test with solc 0.7.5 on ubuntu-latest	4m 17s
Test with solc 0.4.25 on windows-latest	4m 17s
Test with solc 0.5.7 on windows-latest	4m 48s
Test with solc 0.6.12 on windows-latest	3m 38s
Test with solc 0.7.5 on windows-latest	4m 39s
	1h 0m 32s

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