Prefix packet and acknowledgement commitments with a protocol version byte

[AdityaSripal]

If we prefix packet and acknowledgement commitments with a version byte, then we can easily differentiate between different protocol versions.

By looking at the first byte, we know which version the packet is committing to. For IBC v2, we can prefix the packet and acknowledgement commitment by the byte 0x02.

Thus, if we ever want to upgrade the protocol and change the provable commitments; we can simply change the first version byte. This will then be rejected by all previous versions; while being accepted and properly committed to by platforms that support the new versions.

I think this is a proposal we should accept and I will put up a PR implementing this.

It's an open question if we need to do the same for receipts.