Fix/Enhance implementation coverage script

[dominikschubert]

Adds better logging and more heuristics. Still pretty raw though and could use some cleanup :sweat_smile:

[coveralls]

Coverage increased (+0.001%) to 91.691% when pulling 50a3cc36ccc81f02fc388c459f1316d87052f5c3 on script_notimplemented-fixes into 03deb69e0708ed1ae11e23924fb8de2f09b569b7 on master.

[steffyP]

I investigated a bit, with latest running locally in docker (the dispatching issue with moto fallback is resolved on master):

• adding inject_host_prefix=False to the client, seems to prevent the EndpointConnectionError (903 STATUS_CONNECTION_ERROR)
• when we increase the timeout (e.g. to 30seconds) almost all timeout/parsing errors seems to be gone - I also had one run were there was no parsing error (902) at all - maybe some of the random generated input also causes issues here?

[dominikschubert]

Closing in favor of #6694