FreeBalance as default reward destination

[Dinonard]

Pull Request Summary

Prevents a potential scenario where user would make reward claiming impossible without first having something staked.

Check list

• added unit tests

[github-actions]

Package	Line Rate	Branch Rate	Health
precompiles/utils/macro/tests	0%	0%	❌
frame/pallet-xvm/src/pallet	33%	0%	❌
frame/pallet-xcm/src	64%	0%	➖
frame/dapps-staking/src	81%	0%	✔
frame/dapps-staking/src/pallet	88%	0%	✔
chain-extensions/xvm/src	0%	0%	❌
frame/xc-asset-config/src	67%	0%	➖
frame/block-reward/src	85%	0%	✔
frame/custom-signatures/src	54%	0%	➖
precompiles/assets-erc20/src	73%	0%	➖
precompiles/dapps-staking/src	93%	0%	✔
precompiles/utils/macro/src	0%	0%	❌
precompiles/utils/src/data	72%	0%	➖
precompiles/substrate-ecdsa/src	78%	0%	➖
frame/pallet-xvm/src	11%	0%	❌
precompiles/xcm/src	84%	0%	✔
precompiles/xvm/src	94%	0%	✔
chain-extensions/types/xvm/src	0%	0%	❌
primitives/xcm/src	66%	0%	➖
precompiles/sr25519/src	79%	0%	➖
frame/collator-selection/src	80%	0%	➖
chain-extensions/types/dapps-staking/src	0%	0%	❌
precompiles/utils/src	72%	0%	➖
chain-extensions/dapps-staking/src	0%	0%	❌
chain-extensions/rmrk/src	0%	0%	❌
chain-extensions/types/rmrk/src	0%	0%	❌
Summary	59% (2559 / 4351)	0% (0 / 0)	➖

Minimum allowed line rate is 50%