Revert "Use managed thread in tests" #706

Job	Run time
downstream	2m 26s
clang-sanitizers (,thread)	2m 54s
linux-compat (manylinux2014-x64)	2m 33s
clang-sanitizers (,address,undefined)	2m 59s
linux-compat (manylinux2014-x86)	2m 10s
linux-compat (fedora-34-x64)	2m 22s
linux-compiler-compat (clang-3)	2m 33s
linux-compat (opensuse-leap)	3m 24s
linux-compiler-compat (clang-6)	2m 54s
linux-shared-libs	2m 29s
linux-compat (rhel8-x64)	3m 5s
linux-compiler-compat (clang-8)	3m 35s
linux-compat (al2-x64)	1m 59s
linux-compiler-compat (clang-9)	3m 32s
linux-compiler-compat (clang-10)	3m 1s
linux-compiler-compat (clang-11)	3m 6s
osx	2m 7s
linux-compiler-compat (gcc-4.8)	2m 21s
windows	4m 12s
linux-compiler-compat (gcc-5)	2m 31s
linux-compiler-compat (gcc-6)	2m 47s
linux-compiler-compat (gcc-7)	2m 25s
windows-shared-libs	4m 8s
windows-vc14 (x86)	2m 20s
linux-compiler-compat (gcc-8)	2m 59s
windows-vc14 (x64)	3m 34s
	1h 14m 26s

Provide feedback