Revert "Revert "Halo: Add master switch to disable Halo (2/2)""

This reverts commit dfc0c71f217e2b6cce2fb97e28b4a10136759f2d.
Revert "Revert "Halo: Add master switch to disable Halo (2/2)" #2"

This reverts commit cfbc37135d4a7fcca8c39f2bc9eb2fd8c13aaebe.