fix: unbond and stake serialization issues

[p0mvn]

Background

There are serialization issues with unbond and stake message.

Empty string for the validator address doesn't get properly serialized and causes signature mismatch issues.

The same problem for zero lock id

Context: https://osmosis-network.slack.com/archives/C03JT90769K/p1694032456473589?thread_ts=1693917419.462069&cid=C03JT90769K

Suggested Design

• placeholder for empty validator address as "none"
• change lock id from 0 to -1 to signify unlocked

Acceptance Criteria

• changes applied
• unit tests updated
• confirmation from @jonator that FE is unblocked receieved

[jonator]

While this is not a perfect solution, it would save us time until telescope can handle nullable values, and is a proven solution when looking back to the "migrate to full range position" message (using lockId -1 instead of 0)

[czarcas7ic]

@jonator, @mattverse should be reaching out to you WRT fixing the serialization on the frontend side, since there was agreement we should do what we can to not solve this chain side

[mattverse]

Left comment in frontend channel

[ValarDragon]

Closing this for now, since its FE libs serialization error.