Add StatsD (updated)

[zainkabani]

Uses the cadence crate for sending metrics to Statsd. Some of the features used from this crate are

• a queueing sink which spawns its own thread to consume metrics on
• a buffered sink which sends metrics in batches to reduce number of network calls
• clients in no-op mode, Unix Socket and UDP mode
• adds support for tagging metrics

Currently only submitting metrics for queries and transactions is implemented