Updates the runner scripts to automatically detect which results from commands are RX vs TX captures
Currently based on file name (whether it starts with rx or tx)
As a result, changed --save-result flag in slice test runner script to --save-rx and --save-tx - and crucially users no longer need to state the name of the relevant capture command
Refactors & updates the implementation of the main functions for the runner scripts - in particular:
Removes a few old unused functions
Moves some checks currently directly implemented in the main function to separate dedicated functions
Moves the parsing & transformation of command-line flag values to dedicated callback functions