Remove StdTxConfig and StdTx.

[robert-zaremba]

Summary

StdTxConfig is marked deprecated and it's not supported any more.

Problem Definition

Since Stargate, whole storage is protobuf based and transactions are build using TxBuilder. We don't even test StdTxConfig. There are few hacks in the code to keep some compatibility for clients:

• intoAny interface and AsAny method
• sdk.TxResponse uses Any for wrapping transaction object -- it should use interface or store the concrete transaction object instead (personally I prefer the latter).
• probably some decoder hacks.

Proposal

Remove the StdTxConfig and related hacks.

This issue is to keep track of this hacks and remove them.

References:

• Clean Any interface Clean Any interface #8167
• Decide on future of amino support Decide on future of amino support #7489

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