Add support for unlimited tests #2033

Job	Run time
Build Echidna on ubuntu-20.04	21m 17s
Build Echidna on ubuntu-20.04	21m 17s
Build Echidna on macos-13	30m 48s
Build Echidna on macos-13	30m 48s
Build Echidna on windows-latest	25m 12s
Build Echidna on windows-latest	25m 12s
Test with solc 0.4.25 on ubuntu-latest	5m 1s
Test with solc 0.4.25 on ubuntu-latest	5m 1s
Test with solc 0.5.7 on ubuntu-latest	3m 25s
Test with solc 0.5.7 on ubuntu-latest	3m 25s
Test with solc 0.6.12 on ubuntu-latest	3m 22s
Test with solc 0.6.12 on ubuntu-latest	3m 22s
Test with solc 0.7.5 on ubuntu-latest	3m 40s
Test with solc 0.7.5 on ubuntu-latest	3m 40s
Test with solc 0.4.25 on windows-latest	6m 47s
Test with solc 0.4.25 on windows-latest	4m 15s
Test with solc 0.5.7 on windows-latest	7m 28s
Test with solc 0.5.7 on windows-latest	7m 28s
Test with solc 0.6.12 on windows-latest	7m 17s
Test with solc 0.6.12 on windows-latest	7m 17s
Test with solc 0.7.5 on windows-latest	8m 40s
Test with solc 0.7.5 on windows-latest	8m 40s
	4h 3m 22s

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