[docs]: client migration guides

[clevinson]

Migration guides for clients wanting to upgrade to interact with a stargate chain.

Should include:

• docs: Add REST endpoints migration guide #8011 upgrading common query/tx pathways from legacy REST to Stargate REST (grpc-gateway)
• upgrading to native grpc client for all query/tx's

Guide should be in multiple languages, ideally:

• Go
• js
• rust?

[amaury1093]

upgrading to native grpc client for all query/tx's

@clevinson In #8257 I added a guide for using gRPC native clients in Go (and links to CosmJS, in JS). I'm not sure if a separate migration guide is useful (would mostly be copy-paste imo). I added a mention in the REST migration guide, to check out the native gRPC guide if the user wants to migrate to gRPC.

If that sounds good to you, I think we can close this issue.

[amaury1093]

Talked with cory offline, closing this.