Client/v2 Custom Broadcast Logic

[julienrbrt]

Introduce custom broadcast logic for client/v2.
With the arrival of server/v2 #21069 and the support for other consensus than CometBFT,
client/v2 needs to get updated.

Currently, client/v2 makes use of the client package from the SDK, and it's client.Context.
Those structs and package assume a CometBFT node.
This cannot be assumed anymore when using server/v2:

• cosmos-sdk/client/broadcast.go

  Lines 23 to 36 in 4666e1d

  	func (ctx Context) BroadcastTx(txBytes []byte) (res *sdk.TxResponse, err error) {
  	switch ctx.BroadcastMode {
  	case flags.BroadcastSync:
  	res, err = ctx.BroadcastTxSync(txBytes)
  	case flags.BroadcastAsync:
  	res, err = ctx.BroadcastTxAsync(txBytes)
  	default:
  	return nil, fmt.Errorf("unsupported return type %s; supported types: sync, async", ctx.BroadcastMode)
  	}
  	return res, err
  	}

There is already work in that direction to abstract client from client/v2.
However, we need to go one step further and make it more extensible to support different broadcast methods / node interface (

cosmos-sdk/client/cometbft.go

Line 12 in 4666e1d

type CometRPC interface {

)

Example usage case: Reecepbcups@49ca35c