Merge in disabled bounties v2

[bedeho]

Background

We now have a bounty v2 pallet, replacing the old one, but since we don't have time to redesign Pioneer or get solid QN support for Carthage or mainnet, we should just introduce it in a disabled state as part of the codebase.

Proposal

1. remove existing old bounty pallet
2. merge in new bounty pallet
3. disable new pallet, in the sense that its not possible to call create_bounty successfully, it should just return an Err instantly.

┆Issue is synchronized with this Asana task by Unito