Duplicate SimApp into callbacks directory (backport #4337)

[mergify]

This is an automatic backport of pull request #4337 done by Mergify.
Cherry-pick of 6610409 has failed:

On branch mergify/bp/release/v7.3.x/pr-4337
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Changes to be committed:
	modified:   modules/apps/callbacks/callbacks_test.go
	modified:   modules/apps/callbacks/ibc_middleware_test.go
	new file:   modules/apps/callbacks/testing/simapp/ante_handler.go
	new file:   modules/apps/callbacks/testing/simapp/app.go
	new file:   modules/apps/callbacks/testing/simapp/contract_keeper.go
	new file:   modules/apps/callbacks/testing/simapp/encoding.go
	new file:   modules/apps/callbacks/testing/simapp/export.go
	new file:   modules/apps/callbacks/testing/simapp/genesis.go
	new file:   modules/apps/callbacks/testing/simapp/genesis_account.go
	new file:   modules/apps/callbacks/testing/simapp/params/amino.go
	new file:   modules/apps/callbacks/testing/simapp/params/doc.go
	new file:   modules/apps/callbacks/testing/simapp/params/encoding.go
	new file:   modules/apps/callbacks/testing/simapp/params/proto.go
	modified:   modules/apps/callbacks/transfer_test.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   modules/apps/callbacks/fee_transfer_test.go
	both modified:   modules/apps/callbacks/ica_test.go

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[srdtrk]

This is needed because v7.3's SendMsg requires the tx to be successful, so we override it. (chain.go is not one of the copied files)

[srdtrk]

This file was not copied in the original PR. I copied it and removed all the functions except SignAndDeliver so that it can be used in overrideSendMsg function

[srdtrk]

Override has made these expSendFailure variables obsolete.

[crodriguezvega]

Looks good to me. Maybe worth mentioning that the argument list of SignAndDeliver has been modified when copying the function over from main, right?

[chatton]

LGTM @srdtrk 👍