Support NumPy smoke on musl CPython

[TRSWNCA]

Summary

This PR adds a musl-CPython NumPy smoke-test path for AlloyStack.

Main changes:

• Add third_party/lib-python-numpy submodule integration for NumPy C-extension sources and import shims.
• Add scripts/build_cxx_musl.py to prepare an x86_64-musl C++ runtime for NumPy C++ sources.
• Add scripts/build_numpy_musl.py to build NumPy C extensions into libnumpy_musl.a.
• Extend user/musl_cpython with a numpy feature that registers NumPy built-in extension modules and required CPython built-ins.
• Add isol_config/musl_cpython_numpy.json and numpy_smoke workload.
• Add scripts/sync_numpy_workloads.sh for syncing NumPy package files/workload into FAT images or mounted image_content.
• Improve musl/CPython/NumPy build logging and make musl CPython build incremental.

Validation

The musl-py workloads and NumPy smoke workload have been run successfully locally.

NumPy smoke result:

numpy v1.25.0 imported
a = [1 2 3 4 5]
b = [10 20 30 40 50]
a + b = [11 22 33 44 55]
a * b = [ 10  40  90 160 250]
matrix:
[[1 2 3]
 [4 5 6]]
transpose:
[[1 4]
 [2 5]
 [3 6]]
matrix multiplication:
[[19 22]
 [43 50]]
mean: 3.0
sum: 15
max: 5

[TRSWNCA]

Reviewed