Implement new golang TX client

[amaury1093]

Problem

The existing client Tx is too confusing, and too tied to the CLI (TxFactory)

Solution

A new TxClient with a well thought out API. ref: #10496 (comment)

txClient := NewTxClient(...)

txClient.StartTx()
govMsgClient := gov.NewMsgClient(txClient)
res, err := govMsgClient.SubmitProposal(...)
if err != nil { ... }
err = txClient.ExecuteBlock()
if err != nil { ... }

// now res has been unmarshaled to MsgSubmitProposalResponse because we executed in block mode
// and we can do something with the proposal ID
txClient.StartTx()
govMsgClient.Deposit(MsgDeposit{ProposalId: res.ProposalId, ...})
...

[tac0turtle]

this will more or less be covered by lens. Once dynamic cosmos is completed there we should opt to push people there

[amaury1093]

Do you think we can replace all instances of our own TxBuilder with lens at some point? Also, wouldn't there be a circular dep sdk<->lens?

[tac0turtle]

oh I thought you meant for external client use. For internal use we can create a simple api for this

[amaury1093]

Yeah the title is confusing. Let's keep this issue closed, we can track this simple API in #8138