Add thread attribute to test harness

[xuchang-vivo]

Summary

• Add a thread attribute to blueos_test_macro::test and only_test so a test body can run concurrently in multiple BlueOS threads.
• Keep existing serial and repeat behavior unchanged when thread is omitted or set to 1.
• Add a kernel unittest that combines thread = 2 with repeat = 2 to validate concurrent execution.

Why

This gives stress and regression tests a direct way to exercise concurrent paths from the test harness without hand-rolling thread startup and completion coordination in each test.

Implementation Notes

• The macro parses repeat and thread together, rejects duplicate or zero values, and uses ConstBarrier plus wait_until/wake for threaded execution.
• Kernel unit tests alias crate as blueos inside the test module only, so the macro can use the same blueos::... paths as external unittest crates.

Testing

• rustfmt test_harness/src/lib.rs kernel/src/lib.rs
• ninja -C out/qemu_mps2_an385.debug kernel_unittest_clippy
• ninja -C out/qemu_mps2_an385.debug kernel/kernel:run_unittest

Expected Output

The new test_harness_thread_attribute unittest is declared as #[test(thread = 2, repeat = 2)], so the kernel unittest run prints one RUN/OK pair per repeat iteration and includes the configured thread count:

[ RUN      ] test_harness_thread_attribute [1/2, threads=2]
[       OK ] test_harness_thread_attribute [1/2, threads=2]
[ RUN      ] test_harness_thread_attribute [2/2, threads=2]
[       OK ] test_harness_thread_attribute [2/2, threads=2]

[xuchang-vivo]

build_prs

[github-actions]

Job is started, see https://github.com/vivoblueos/kernel/actions/runs/25646966663.

[github-actions]

❌ Job failed. Failed jobs: build_and_check_boards (failure), see https://github.com/vivoblueos/kernel/actions/runs/25646966663.

[xuchang-vivo]

build_prs

[github-actions]

Job is started, see https://github.com/vivoblueos/kernel/actions/runs/25647237583.

[xuchang-vivo]

build_prs

[github-actions]

❌ Job failed. Failed jobs: build_and_check_boards (failure), see https://github.com/vivoblueos/kernel/actions/runs/25647237583.

[github-actions]

Job is started, see https://github.com/vivoblueos/kernel/actions/runs/25647307332.

[github-actions]

✅ All jobs completed successfully, see https://github.com/vivoblueos/kernel/actions/runs/25647307332.