Support get apf capabilities from network_stack shell command

This utility reads output of cmd network_stack apf ${iface_name}
capabilities. This is needed for the tests to skip if the apf
version is too old.

Test: atest NetworkStaticLibHostPythonTests
Bug: 352132428
Change-Id: I1f8b523c3e6f687c2e919993bc18392dc25dbbf7
2 files changed