With #960 we got a big blocker for big CI setups (hundreds of parallel CI jobs) out of the way to use SimpleCov.collate and generate a report.

We still have plenty of optimization potential left to make SimpleCov faster and more efficient for those setups:

• allow saving of .resultset.json without going through SimpleCov::Result or reducing the overhead of SimpleCov::Result massively, Improve performance of collate & reduce memorty consumption #960 already massively reduced how often we instantiate it but as its core we only want to dump the collected coverage data into .resultset.json which we should be able to do easily without it
• make it easy to run with no formatter, right now we recommend to run with a simple formatter but it'd be even better to run with no formatter at all - all the separate CI jobs don't need to go through the overhead of generating a full report, only the final one with collate should. I'm not even sure if we can specify formatter nil or formatters [] right now.
• Package up these settings in a new profile for easy usage