Create network folders for branch removal

[ross-spencer]

We can manage this repo more effectively without using multiple branches. We use folders to delineate network instead. Mainnet and preview are the only ones used as preprod isn't being used in Orcfax deployments right now.

@george-orcfax @gchartier <-- preparing to make this change this week if possible. Let me know if you have any preferred ways for me to coordinate this.

Connected to: https://github.com/orcfax/issues/issues/197

[george-orcfax]

Just let me know when you merge it, so that I can change immediately the URL in the monitoring.

[ross-spencer]

Thanks George!

@gchartier anything can be impacted your end?

[gchartier]

Looks great, just need to know when you plan to merge so I can push my code update to the index. 👌

[gchartier]

Actually, I just thought of something that would make sense to change now while we're at it:

If we plan to continue using this same repo moving forward and for different feed types in addition to CER feeds, then I think the name of the repo should probably not be cer-feeds.

Perhaps active-feeds or simply feeds would be a better name?

If we change the name then that makes the feeds folder in the repo redundant and can just have folders for each network at the top-level instead.