Tendermint client does not support batched RPC requests

[tarcieri]

Copying/pasting this from tendermint/tmkms#301 as reported by @devashishdxt

Batched RPC requests are supported by tendermint since v0.31.6

tendermint/tendermint#3534

[thanethomson]

Do we want similar semantics to how the Tendermint RPC client batch API works? See github.com/tendermint/tendermint/rpc/client/examples_test.go.

Essentially these semantics require that we:

1. Use the client to create a batch (with similar methods as the client; will derive the target address from the client)
2. Call methods on the batch that correspond to requests (e.g. broadcast_tx_async). This caches the calls in the batch.
3. Call a send method that serializes the requests and returns an array of results, with each result corresponding to a cached request.

Once we agree on semantics, I can look at coding this in the coming weeks.

[tarcieri]

@thanethomson I don't know the answers to your questions, but will say that the current client probably needs some refactoring in general, especially with the recent Rust developments in async/await support. I'm happy to field questions about that, and it seems like you may want to use futures to implement some of what you're describing.

[romac]

This was likely closed by mistake because a commit in 592 contained #1.