MB-16181: Add Collections Filter classes and test

MB-16181: Add Collections Filter classes and test

Two classes exist for filtering.

Collections::Filter
Collections::VB::Filter

The idea is that a DCP producer will establish a Collections::Filter
that lives for the lifetime of the DCP producer.

As the DCP producer creates streams, a Collections::VB::Filter is
assigned to the stream which contains the real set of collections to
filter (and also the actual "filter" function).

Change-Id: I2f35b1698ce977116486a2e6940437eee25faef1
Reviewed-on: http://review.couchbase.org/78137
Reviewed-by: Dave Rigby <daver@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>