Fixes #7749 - allow using logger in log_halt helper

(cherry picked from commit 2fe082ea514e6f86cba338a4b0bcccd452a542c0)
fixes #7596 - validate plugin dependencies when loading, various fixes

(cherry picked from commit 20b9f969fcc42e06be7daeb587bc4f485d9d2b17)
fixes #7297 - corrected name of DNS namespace in virsh error handlers

Refactored DNS and DHCP specifics back into the respective modules

(cherry picked from commit b32f2f777c5e23119f3daced9c96432d08d5bef7)