move to containers/composefs-storage-experimental ?

[cgwalters]

We discussed this on chat, but writing a ticket - we could move to the containers/ GH organization, which is a big "open tent" place for this type of stuff, and is obviously where composefs is now.

[allisonkarlitskaya]

We just agreed in a call:

• this repository will become containers/composefs-rs
• we will delete the rust/ subdirectory of https://github.com/containers/composefs
• the composefs-sys crate will stop existing
• the crate in this repository will be renamed to composefs
• we will review code from the existing composefs crate for merging into this project