refactor: begin to provide formal specs for test operations
refactor: begin to provide formal specs for test operations

Test operations until now have been built dynamically based on key
checking on the arguments object passed in. This approach works
but is very brittle. This commit introduces a new way of resolving
the test operation through a more formal specification that all
operations will eventually be migrated to.

mongodb/node-mongodb-native,mongodb/node-mongodb-native,mongodb/node-mongodb-native,mongodb/node-mongodb-native