security/py-bro-pkg: Rename to security/py-zkg and update to 2.0.0

The project name of upstream has changed from "Bro" to "Zeek". This also
affects the repositories and offered packages.

• Rename the port to security/py-zkg
• Adapt the text references in COMMENT and pkg-{descr,message} accordingly.
• Update to 2.0.0

Changelog:

https://github.com/zeek/package-manager/blob/v2.0.0/CHANGES

PR: 237634
Submitted by: Shirkdog <mshirk@daemon-security.com> (maintainer)
Reviewed by: koobs