Add option to disable channel priority

[ZzEeKkAa]

Some option to disable channel priority would be useful.
https://conda.io/projects/conda/en/latest/user-guide/tasks/manage-channels.html

[eitsupi]

Thanks for opening this!
Could you make a PR to add that?

[maresb]

I am supportive of this, but I think it would be more useful to add a more general mechanism for defining a custom .condarc. Then not only do we have a solution for changing channel priority, or making any other .condarc-based adjustment.