Bluetooth: BAP: Broadcast assistant shell treat PA sync as bool

Modify the broadcast assistant commands that take the PA sync argument
so that it is treated as a bool. This allows users to use
"true", "on", "1" or "0x01" for true values and "false", "off", "0"
for false values.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>