Add missing `anteHandlers` methods in `newLegacyCosmosAnteHandlerEip712`

[omritoptix]

2 points here:

1. The newLegacyCosmosAnteHandlerEip712 looks to handle Cosmos transactions, same as newCosmosAnteHandler with the only difference that legacy handler can handle transactions signed with Ledger. If they must be equivalent in everything else, probably the legacy handler should also use ante.NewExtensionOptionsDecorator and delayedack.NewIBCProofHeightDecorator (these two are used in "normal" handler but not in "legacy" one)

2. please double-check that the ante.NewExtensionOptionsDecorator is intended to be configured like it is now. The checker is nil and, by looking at the config structure, someone could think that it allows all extensions but it forbids any of them