Check status after script/command execution

[maltanar]

Many transformations and utility functions in FINN call external commands such as g++, vivado and vivado_hls without checking the return status. If the called command fails, the FINN transformation won't be aware of this. Assertions should be introduced on the return status whenever an external command is called.

[mumallaeng]

Opened #1662, which routes the unchecked subprocess.Popen(...).communicate() call sites through launch_process_helper(check=True) so a failed vivado/vitis/vitis_hls/g++ invocation raises instead of being silently ignored.