Add gRPC for ibc-transfer/getEscrowAccount

[ghost]

Summary

Per #9383, There has been a cli command added to get the escrow account for an IBC channel. It would be most helpful to also have the gRPC query for it as well.

Problem Definition

Programmatic use of the sdk can not take advantage of CLI commands. This is a case where the added command can be useful via grpc.

Proposal

• Add getEscrowAccount to the ibc/transfer query grpc
• Would need to backport to https://github.com/cosmos/ibc-go as well

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[ghost]

I understand that the address is manually constructed with no interaction from the chain, but with the Version constant being just a string that could be updated in the future, it would be nice to have official support instead of having to worry that it has changed in the next release.