[Refactor]: x/auth/tx and x/tx should converge on gogoproto usage.

[kocubinski]

There is duplicate logic in both x/tx/decode and the x/auth/tx packages. Since the decision to support gogoproto throughout the SDK (as specified in core/transaction below)

cosmos-sdk/core/transaction/transaction.go

Line 8 in 1f06f5b

Msg = gogoproto.Message

These two packages can be simplified and collapsed into one simple implementation in x/tx. An initial exploration of this was done here in #20424 and integrated in #20428.

The result will be a lot of deleted code and much less mental overhead when reasoning about transactions in the SDK. The signing code in x/tx can and should remain the same, as shown in #20424 reflection over gogotypes as input is possible through the use of dynamic messages.

[noelukwa]

@tac0turtle i would like to take on this

[tac0turtle]

yes, we would love the help ❤️

[kocubinski]

@noelukwa Great, #20424 has some preliminary work for it.