Start to modernize the remaining old simcalls related to comms

Start to modernize the remaining old simcalls related to comms
+ refactor wait, test, waitany, and testany at the activity level
+ use observers for all the simcalls related to these operations
+ add 2 new examples that allows to test or wait for the completion of
any kind of activities stored in a single vector
+ simplify another example thanks to that
+ implement the to_string and dot_label functions in the observers
instead of in mc::Api

This (big) commit breaks the MC has the dependency check still mixes
old and modern simcalls and is thus borken. This is a work in progress
for the greater good, and towards SG4.