Add circuit breaker on heap memory usage for file cache

[adnapibar]

Coming from #6227
Implement a circuit breaker to prevent the file cache for searchable snapshot causing an OutOfMemoryError. The breaker will put a limit on the cache for how much memory it can use. CircuitBreakerException will be thrown for requests that will cause the cache to use more heap memory than specified.

[kotwanikunal]

Two possible solutions were assessed -

1. Add a new child memory breaker which will keep track of memory usage by the file cache
2. Use a pre-existing child breaker to keep track of total memory usage (tracked by the parent breaker)

Approach 1 would be ideal if there was a fixed size of an entry for the cache, but it varies depending on the platform architecture, OS, JVM variations.
Approach 2 solves the problem by keeping tracking of total memory usage instead of individual entries, and checking the breaker as soon as an entry is added.