rt-app ignores invalid task names

[douglas-raillard-arm]

Invalid task names are ignored by rt-app, instead of aborting. Since that's a user setting, rt-app should either honour it or reject it like for some other settings. The current behaviour creates some issues in automated environments as rt-app keeps going and leads to a trace that does not contain the expected task names. This creates further non obvious errors down the line.

Since the maximum allowed name length is not easily predictable anymore (depending on the suffix size used), it would be best to treat that as an error when non-default is used.