Burn stale rewards

[Dinonard]

Pull Request Summary

This is in response to request made by ShidenDAO to support burning of stale developer rewards.

In case developer's contract gets unregistered, they can still claim their old rewards. Before this update, this was possible indefinitely, and some devs would never do this.

With this update, a new extrinsic call is introduced which will burn unregistered contract's unclaimed rewards.

Summary:

• the call needs to be made with root privileges
• in case contract is still registered, the call will fail
• in case reward was already claimed, it cannot be burned
• once burned, reward cannot be claimed
• the burn is executed per era (same as rewards are claimed)
  • in case multiple eras need burning, multiple calls will be required (e.g. via batch call)

Check list

• [x] added unit tests
• [x] updated documentation

[github-actions[bot]]

Package	Line Rate	Branch Rate	Health
precompiles/assets-erc20/src	73%	0%	➖
primitives/xcm/src	66%	0%	➖
chain-extensions/xvm/src	0%	0%	❌
chain-extensions/dapps-staking/src	0%	0%	❌
frame/xc-asset-config/src	67%	0%	➖
frame/collator-selection/src	80%	0%	➖
precompiles/sr25519/src	79%	0%	➖
frame/pallet-xvm/src/pallet	33%	0%	❌
precompiles/substrate-ecdsa/src	78%	0%	➖
frame/dapps-staking/src	81%	0%	✔
precompiles/dapps-staking/src	93%	0%	✔
precompiles/utils/macro/src	0%	0%	❌
precompiles/xcm/src	84%	0%	✔
precompiles/utils/src/data	72%	0%	➖
frame/pallet-xcm/src	64%	0%	➖
frame/block-reward/src	85%	0%	✔
chain-extensions/types/rmrk/src	0%	0%	❌
frame/dapps-staking/src/pallet	87%	0%	✔
chain-extensions/types/xvm/src	0%	0%	❌
frame/pallet-xvm/src	11%	0%	❌
chain-extensions/rmrk/src	0%	0%	❌
chain-extensions/types/dapps-staking/src	0%	0%	❌
frame/custom-signatures/src	54%	0%	➖
precompiles/utils/src	72%	0%	➖
precompiles/xvm/src	94%	0%	✔
precompiles/utils/macro/tests	0%	0%	❌
Summary	59% (2585 / 4385)	0% (0 / 0)	➖

Minimum allowed line rate is 50%