Add serial test execution support #308

Job	Run time
test (1, default, windows-latest)	4m 30s
test (pre, x86, windows-latest)	5m 4s
test (pre, default, windows-latest)	4m 17s
test (min, x86, ubuntu-latest)	3m 21s
test (1, x86, windows-latest)	4m 33s
test (1, default, ubuntu-latest)	3m 31s
test (nightly, default, ubuntu-latest)	4m 15s
test (min, x86, windows-latest)	4m 26s
test (nightly, default, macOS-latest)	3m 43s
test (nightly, x86, ubuntu-latest)	5m 17s
test (min, default, macOS-latest)	2m 6s
test (min, default, windows-latest)	3m 36s
test (pre, x86, ubuntu-latest)	4m 12s
test (nightly, default, windows-latest)	4m 57s
test (1, x86, ubuntu-latest)	3m 59s
test (pre, default, macOS-latest)	3m 49s
test (nightly, x86, windows-latest)	5m 20s
test (min, default, ubuntu-latest)	3m 6s
test (1, default, macOS-latest)	3m 19s
test (pre, default, ubuntu-latest)	3m 49s
	1h 21m 10s

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