Add airlift stats

[oneonestar]

Description

Part of #41.

Abstract the stats counting using ProxyHandlerStats.
This is similar to the implementation inTrino, see: CallStats.java

Add airlift stats in parallel with io.dropwizard.metrics.
Can't remove io.dropwizard.metrics right now because we can't export airlift stats in REST API under Dropwizard.

After switch to Airlift, ProxyHandlerStats and CounterStat will stay.
com.codahale.metrics.Meter and Environment will be gone.

	JMX	JMX using RESTful API	JMX Provider
Before this PR	Dropwizard metric	Dropwizard metric (localhost:9082/metrics)	Dropwizard and MetricRegistry
After this PR	Dropwizard metric + Airlift stats	Dropwizard metric (localhost:9082/metrics)	Dropwizard and MetricRegistry
After migration to Airlift	Airlift stats	Airlift stats (/v1/jmx)	Airlift:jmx and Airlift:jmx-http

JMX can be accessed using RMI (by jconsole or jvisualvm).
Airlift stats (new):

Dropwizard metrics (existing):

Release notes

(x) This is not user-visible or is docs only, and no release notes are required.