Audit use of abort() and remove where possible

During investigation of MB-21475 it was noted that we still have a number of abort() calls in the codebase. The intent was to replace such uses with throwing exceptions (see https://github.com/couchbase/memcached/blob/master/docs/ErrorHandling.md) however while the cb_assert() calls were addressed, abort was not

We should audit the use of abort, and remove where possible, replacing with exceptions (e.g. std::logic_error.