sysutils/bricoler: Add: Utility for running FreeBSD src development

bricoler is a utility for running FreeBSD src development workflows. The basic
idea is to simplify common src development tasks by providing a framework to
wrap operations like:

• building a FreeBSD src tree,
• constructing a VM image from the output of a build,
• booting the VM image,
• running things in the guest once it has booted.