Stabilize `archive_*` RPC methods

[jsdw]

Let's aim to stabilize the archive_* methods in their current form. Doing so will:

• Encourage more people to try out these methods without fear of them changing.
• Allow tooling and other libraries to target them for the same reason.
• Lead to more complete feedback which we can take into account for a future v2 set of methods (if necessary).

I think that the methods as they stand may not be perfect, but provide a "good enough" experience.

if there are any crucial omissions, please do leave feedback here and we can aim to address them. Otherwise, I think that we should prevent the perfect from being an enemy of the good, and stabilize these sooner rather than later so that we can start getting some proper usage of them :)

[Polkadot-Forum]

This issue has been mentioned on Polkadot Forum. There might be relevant details there:

https://forum.polkadot.network/t/stabilizing-the-archive-rpc-v2-methods/12058/1

[jsdw]

Closed by #167