Create version of benchRun() which can be used with embedded

This makes it possible use our existing https://github.com/mongodb/mongo-perf tests as performance tests for embedded. We can likely get away with creating separate executables for each mongo-perf test case that uses ServiceEntryPointEmbedded, embedded::initialize(), and DBDirectClient (instead of DBClientConnection) to perform operations.

Note: We'll also need to remove or split out the "check" function as it requires linking in the JavaScript engine.