Rename Lotus RPC endpoint versions to reduce developer confusion

[eshon]

Current endpoints:

https://filecoin.chain.love/rpc

• v0 stable - should anyone be using this anymore at all? If it's deprecated should it be removed?
• v1 unstable - can we call this something other than 'unstable'? It's actually the recommended one right now
• v2 experimental - this is the only F3-aware API currently and if we want exchanges and other partners to adopt F3, after some more testing feedback it would be ideal to move F3-semantics to v1