Add a fungible packet memo namespacer

[danwt]

We now use a namespaced json in the fungible memo for

• sending denoms hub->ra
• accepting genesis transfers ra->hub

and maybe other future use cases

Regular users or third party code might also want to use it. We don't want to place restrictions on them or make assumptions, so we should assume that their memo can be arbitrary.

Therefore we need something to take their memo, namespace it according to our rules, and then un-namespace it at the other end

[danwt]

See some example code here https://github.com/dymensionxyz/dymension/blob/9348869e92155ca106a853ab60ec3ba1ea2ee8b3/utils/memo/memo.go#L12-L48

[danwt]

see also https://github.com/dymensionxyz/dymension/blob/02eb0c108fa589a81a9a830f5cc2455f58756666/utils/map/funcs.go#L13-L39

[danwt]

see https://github.com/dymensionxyz/fungible-packet-memo-namespace-middleware

Needs to be tested I'm not sure if it breaks acks It shouldn't do..