Shrink on one worker #1963

Job	Run time
Build Echidna on ubuntu-20.04	5m 20s
Build Echidna on macos-13	42m 49s
Build Echidna on windows-latest	27m 41s
Test with solc 0.4.25 on ubuntu-latest	5m 3s
Test with solc 0.5.7 on ubuntu-latest	3m 28s
Test with solc 0.6.12 on ubuntu-latest	3m 30s
Test with solc 0.7.5 on ubuntu-latest	3m 52s
Test with solc 0.4.25 on windows-latest	5m 34s
Test with solc 0.5.7 on windows-latest	4m 7s
Test with solc 0.6.12 on windows-latest	6m 16s
Test with solc 0.7.5 on windows-latest	6m 22s
	1h 54m 2s

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