Using cmake and c++ gives us an opportunity to use ctest to build unit test code. If we keep the S3 interactions standalone as a separate class, it gives us the opportunity to test them without building the rest of the extension (and WiredTiger).

We will put a timeboxed effort into achieving the goal of adding some unit testing with this ticket. The unit test could be limited to listing the buckets, and hence could be started just after WT-8653 gets done.