[Feature] Add support for HLL extension.

[RyanWalker277]

HLL (Hyper LogLog) is a postgres extension which is used to optimize count queries. It can measure the cardinality of a dataset of billions of items in just a few milliseconds. We are using it in https://github.com/bharatsahaiyak/inbound-js/ through an external image (https://github.com/citusdata/postgresql-hll). Adding the support here would be useful and remove this external dependency.

Refrences:

https://github.com/citusdata/postgresql-hll