Include /etc/containers/registries.conf in must-gather

[BrendanFishback]

Feature and motivation

It would be ideal if the /etc/containers/registries.conf file from all nodes was captured during the MAS must-gather collection. This file is important for troubleshooting airgapped installations.

Usage example

This enhancement would avoid support from having to request the file manually from a client, and speed up support case resolution.