databases/foundationdb-devel: [NEW PORT] distributed ACID transactions

FDB 7.x has a new cmake-derive build system, and upstreamed patches that
already supports C client bindings for other languages. While the
upstreamed patches are still under development, this port allows
FoundationDB users and committers to easily test and work with FreeBSD,
and also enables FreeBSD-based clients to work out of the box.

Approved by: vanilla
Sponsored by: SkunkWerks, GmbH
Differential Revision: https://reviews.freebsd.org/D23287