test: cover GetNumThreads default #2908

Job	Run time
lint / clang-format	11s
lint / python-lint	7s
ubuntu / ubuntu-gcc-build-debug (ubuntu-24.04)	1m 3s
ubuntu / ubuntu-gcc-build (ubuntu-24.04)	1m 7s
ubuntu / ubuntu-gcc-build (ubuntu-24.04-arm)	2m 44s
ubuntu / ubuntu-clang-build (ubuntu-24.04)	1m 11s
mac / macos-clang-build	2m 6s
mac / macos-clang-build-debug	1m 59s
ubuntu / ubuntu-clang-build (ubuntu-24.04-arm)	1m 41s
windows / windows-msvc-build	2m 48s
windows / windows-msvc-build-debug	6m 7s
windows / windows-clang-build	2m 48s
ubuntu / ubuntu-clang-test (ubuntu-24.04)	1m 4s
ubuntu / ubuntu-clang-test (ubuntu-24.04-arm)	1m 24s
ubuntu / ubuntu-clang-sanitizer-build (ubuntu-24.04)	1m 16s
mac / macos-clang-test	1m 26s
ubuntu / ubuntu-gcc-test (ubuntu-24.04)	1m 20s
ubuntu / ubuntu-gcc-test (ubuntu-24.04-arm)	1m 9s
windows / windows-clang-test	53s
windows / windows-msvc-test	51s
ubuntu / ubuntu-clang-test-extended	0s
ubuntu / ubuntu-clang-sanitizer-test (ubuntu-24.04)	1m 1s
mac / macos-clang-test-extended	-1s
ubuntu / ubuntu-gcc-test-extended	0s
ubuntu / ubuntu-gcc-build-codecov	0s
windows / windows-clang-test-extended	0s
ubuntu / ubuntu-clang-sanitizer-test-extended	0s
windows / windows-msvc-test-extended	0s
perf	0s
	34m 15s

Provide feedback