Remove @Beta from BloomFilter, Funnel(s), and Hasher

[Xaerxess]

In #3284 several classes in com.google.common.hash were promoted from @Beta, most notably Hashing and HashFunction. @netdpb also mentioned there was a review of "all @Beta APIs with the intention of removing @Beta from all that have no serious outstanding API issues" (see this comment.

Having said that, BloomFilter, related Funnel(s) and PrimitiveSink still remain in @Beta, so please consider promoting these classes — they seem widely used and pretty stable (they're a part of Guava since version 11.).

Related feature request: #2226 (extracting ProbablisticFilter interface).

[artonu]

@kluever Please consider Hasher as well.