test: cover GetNumThreads default #2900

Job	Run time
lint / clang-format	7s
lint / python-lint	7s
mac / macos-clang-build	2m 23s
ubuntu / ubuntu-gcc-build-debug (ubuntu-24.04)	2m 44s
ubuntu / ubuntu-clang-build (ubuntu-24.04-arm)	3m 6s
ubuntu / ubuntu-clang-build (ubuntu-24.04)	2m 27s
ubuntu / ubuntu-gcc-build (ubuntu-24.04)	2m 13s
mac / macos-clang-build-debug	1m 57s
windows / windows-msvc-build-debug	6m 45s
ubuntu / ubuntu-gcc-build (ubuntu-24.04-arm)	3m 50s
windows / windows-msvc-build	2m 21s
windows / windows-clang-build	8m 1s
mac / macos-clang-test	2m 53s
ubuntu / ubuntu-clang-test (ubuntu-24.04-arm)	5m 14s
ubuntu / ubuntu-clang-test (ubuntu-24.04)	4m 55s
ubuntu / ubuntu-clang-sanitizer-build (ubuntu-24.04)	1m 21s
ubuntu / ubuntu-gcc-test (ubuntu-24.04-arm)	5m 29s
ubuntu / ubuntu-gcc-test (ubuntu-24.04)	5m 35s
windows / windows-msvc-test	0s
windows / windows-msvc-test-extended	0s
ubuntu / ubuntu-clang-sanitizer-test (ubuntu-24.04)	1m 50s
mac / macos-clang-test-extended	2m 8s
ubuntu / ubuntu-clang-sanitizer-test-extended (ubuntu-24.04)	1m 37s
ubuntu / ubuntu-clang-test-extended (ubuntu-24.04-arm)	4m 5s
ubuntu / ubuntu-clang-test-extended (ubuntu-24.04)	4m 2s
windows / windows-clang-test-extended	0s
windows / windows-clang-test	0s
ubuntu / ubuntu-gcc-test-extended (ubuntu-24.04-arm)	2m 56s
ubuntu / ubuntu-gcc-test-extended (ubuntu-24.04)	2m 38s
ubuntu / ubuntu-gcc-build-codecov	3m 41s
perf	0s
	1h 24m 25s

Provide feedback