refactor(mongo-credentials): support accepting `auth` from parser
refactor(mongo-credentials): support accepting `auth` from parser

The connection parser outputs auth information in a specific format
which the current `MongoCredentials` does not properly parse. This
allows us to pass the output of that parsing directly into the ctor

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