FIFO uniqueness logic prevents wrapper scripts for test applications

[andy31415]

Our current logic is to suffix PID to fifo names. Like /tmp/chip_rvc_fifo_....

However this means that if we create a wrapper launcher script for apps (like for example to use RR or setup environment variables like for coverage output) the scripts take the "shell launcher PID" while the app uses its own "PID".

This results in applications failing to actually communicate. We need to:

• tests should detect if FIFO file exists before writing (otherwise this was super hard to debug)
• applications should somehow take in the FIFO suffix to use. Either command line arguments (then script CI arguments can control this) or environment variables or something else passed through.