Add an abstraction that provides a standard manner to retrieve a
statistics snapshot of a cache.

Specific implementations for JSR-107, ehcache, hazelcast, guava and
concurrent map are provided. At the moment the size of the cache and
the hit/miss ratios are recorded. Cache metrics are exposed via the
`cache.` prefix followed by the name of the cache. In case of conflict,
the name of the cache manager is added as a qualifier.

It is possible to easily register a new CacheStatisticsProvider for an
unsupported cache system and the CacheStatistics object itself can be
extended to provide additional metrics.

See gh-2633
Closes gh-2770