Allow setting individual breakers to "noop" breakers

This adds a NoopCircuitBreaker, and then adds the dynamic settings
`indices.breaker.fielddata.type` and `indices.breaker.request.type`,
which can be set to "noop" in order to use a breaker that will never
break, and incurs no overhead during computation.

This also refactors the tests for the CircuitBreakerService to use
@Before and @After functions as well as adding settings in
ElasticsearchIntegrationTest to occasionally use NOOP breakers for all
tests.
Can this just be `ensureGreen(TimeValue.timeValueSeconds(10), "ramtest");`?