[migrations] Migration from static `Lanes` to dynamic lanes (`master`)

[bkontur]

Actually, we defined hard-coded lane between AssetHubs (Ro/We, K/P), but we need to have migration from this static to dynamic lanes stored on-chain.

I think we don't need this for Rococo/Westend, we can to governance calls (but maybe it would be cool to test migration).
But surely, we need this for Kusama/Polkadot, because when we upgrade runtimes to the dynamic lanes, we cannot wait for follow-up governance calls to establish lane between AssetHubs again.

• check what everything needs to be migrated
  • storage
  • laneIds
• prepare migration
• add migration to the polkadot-fellows repo