Improve SHM Transport logging messages

[JLBuenoLopez]

Some opened tickets are complaining that the SHM Transport initialization failure logged messages are unclear from a user point of view. For instance #2790, #2003.

I am opening this ticket to keep track about improving the messages so they can be more helpful to the user.

[aditya2592]

I had a question about the fastdds shm clean command and the code in clean.py. On my ubuntu system, FastDDS with SHM generates the folllowing file types

-rw-r--r--  1 root root        32 Jan 19 21:16 sem.fastrtps_port7438_mutex
-rw-r--r--  1 root root         0 Jan 19 21:16 fastrtps_port7439_el
-rw-r--r--  1 root root     52416 Jan 19 21:16 fastrtps_port7439

However clean.py only cleans up files ending in _el and files like fastrtps_port7439 are left behind. Is there a reason behind that?