util-logging: make QueueingHandlerTest more robust

Problem

QueueingHandlerTest has occasional failures in CI.

Solution

Use scalatest's Eventually and a longer PatienceConfig
to make the tests more robust.

RB_ID=527617
util-thrift: add unit tests for {Binary,Compact}ThriftCodec

RB_ID=527793
util-core: Introduce new API method Future.collect(Map)

This PR also does Java-friendly refactoring. It makes a single API
enptrypoints for both of use-cases:

 - in Java is `Futures` that takes Java collections
 - in Scala is `Future` that takes Scala collections

RB_ID=524473
util-hashing: Add more tests for the Hashable object

Problem

util-hashing has bad test coverage.

Solution

Add more tests for Hashable, and move the distribution test file
in the 'test' subdirectory.

RB_ID=530925