Read preference backward compatibility

In earlier 3.0-dev commits support was removed for the secondary_acceptable_latency_ms and tag_sets properties on the client, database, and collection objects, options to find(), and secondaryAcceptableLatencyMS as a URI option. The goal of this ticket is to add that support back for backward compatibility. Use of any of these features will raise DeprecationWarning.

Related earlier commits:
https://github.com/mongodb/mongo-python-driver/commit/2f862072463bfcb990af5b5144522f100b857c4e
https://github.com/mongodb/mongo-python-driver/commit/e0b52baf8e1bd76972043fdfcecda77d01185831