This change adds a module within pw_cli that provides a function for
running a subprocess and capturing its stdout and stderr to the main
pw log. A new log level is defined for the captured output.
The pw_unit_test runner script is updated to use this function instead
of running its subprocess directly.
The pw command is updated to run its subcommand in an async context,
preventing subcommands from needing to create their own. Fully
synchronous subcommands continue to function transparently to this.
Change-Id: Ia9efb1fbda8a38ef91a0e14113929711038710a8
This renames pw_cmd to pw_cli, since our plan is for the cli module to
contain general command line interface related tooling, rather than just
the pw_cmd itself.
Change-Id: I1dc7185db25b89d725601ac5d47e0793ea907bf1
