sysutils/vm-bhyve-devel: add new port

Contrary to the sysutils/vm-bhyve port which tracks releases,
this port will track the head of the main branch. The main reason
is that upstream has become stale in creating releases. This way
we atleast get some improvements that have not yet been included
in a release. Last release dates from January 2020.

Changes: https://github.com/churchers/vm-bhyve/compare/6385042...ec0e12e

Reviewed by: 0mp philip
Differential Revision: https://reviews.freebsd.org/D35760