Autopilot to pass custom memo in the forwarding IBC packet

[arlai-mk]

Background

When we use autopilot's "ibc_receiver" prop in stakeibc's LiquidStake action (so that the newly minted stAsset can be forwarded to another IBC chain), a static memo is passed in the resulting MsgTransfer message: "autopilot-liquid-stake-and-forward"
https://github.com/Stride-Labs/stride/blob/v21.0.0/x/autopilot/keeper/liquidstake.go#L138

Chains like Osmosis have IBC hooks that would allow automated swap (for instance, stATOM to ATOM), and they require a specially crafted memo within the IBC packet.
If we wanted to automate swapping after liquid staking, we would need to be able to craft a memo that would be passed to the next hop (a bit like the "next" field of the packet-forward-middleware).

This would be very useful, especially if combined with LSMLiquidStake in Autopilot as described here: #1169.
It would unlock the ability to immediately redeem staked ATOM into ATOM on the Cosmos Hub in two transactions:

• TX # 1: Tokenize Shares from already staked ATOM
• TX # 2:

1. IBC to Stride with the action LSMLiquidStake, IBC receiver on Osmosis, custom IBC memo
2. Stride automatically mints stATOM
3. Stride automatically sends it to Osmosis, with the custom memo to convert to ATOM
4. Osmosis automatically swaps stATOM for ATOM (query from the custom memo)
5. Osmosis automatically sends ATOM to Cosmos Hub

Suggested Design

I would like to suggest:

• Adding IbcMemo to StakeibcPacketMetadata so we can pass a custom string in the ibc_memo field.
  Suggestion to include in StakeibcPacketMetadata as: IbcMemo string `json:"ibc_memo,omitempty"`
• If autopilotMetadata.IbcMemo is not empty, it can be added here: https://github.com/Stride-Labs/stride/blob/main/x/autopilot/keeper/liquidstake.go#L138. If it's empty, we can keep "autopilot-liquid-stake-and-forward"

Acceptance Criteria

This should be pretty straightforward, but if you agree that this could be a nice-to-have feature, please let me know and I'll create a PR for it.

Thank you.