pallet-child-bounties index child bounty by parent bounty (#6255)
Resolves https://github.com/paritytech/polkadot-sdk/issues/5929 Migrates `ChildBountyDescriptions` to be indexed instead of unique child bounty id unique per all child bounties in the pallet to be unique per every parent bounty. Migrates `(ParentBounty, ChildBounty)` keys inside `ChildBounties` storage item to use new `ChildBounty` ids starting from `0`. @paritytech/frame-coders --------- Signed-off-by: Oliver Tale-Yazdi <[email protected]> Co-authored-by: DavidK <[email protected]> Co-authored-by: muharem <[email protected]> Co-authored-by: Oliver Tale-Yazdi <[email protected]>