[Anvil] State injector

[alindima]

Add a mechanism that allows injecting arbitrary key/values into a running substrate blockchain. We need to hack the Backend implementation.
Includes support for the following rpcs:
anvil_setBalance
anvil_setChainId
anvil_setCode
anvil_setNonce
anvil_setStorageAt

[iulianbarbu]

Will add a reference for our today's discussion: we might need here to add anvil_setChainId too, as part of the state injector enabled RPCs. I can look into this issue since it is a dependency already for my work at #241, if no one takes it.

[AlexandruCihodaru]

Currently Anvil allow setting time to a timestamp older than the timestamp of the last produced block.
anvil-polkadot however does not allow it and when trying to set the time in the past and mine a new block the new block will have a timestamp = previous_timestamp + 1. According to an offline discussion with @alindima this happens because

let next_time = cmp::max(data, Now::<T>::get() + T::MinimumPeriod::get());

Hence for a forked chain we will need the state injector to have block times smaller than MinimumPeriod

[alindima]

Currently Anvil allow setting time to a timestamp older than the timestamp of the last produced block. anvil-polkadot however does not allow it and when trying to set the time in the past and mine a new block the new block will have a timestamp = previous_timestamp + 1. According to an offline discussion with @alindima this happens because

let next_time = cmp::max(data, Now::::get() + T::MinimumPeriod::get());
Hence for a forked chain we will need the state injector to have block times smaller than MinimumPeriod

Moreover, we need to use the state injector for the timestamp so that we can go back in time

[iulianbarbu]

Moreover, we need to use the state injector for the timestamp so that we can go back in time

Do you mean for the Now storage item? I think the Now storage item would need to be modified whenever we want to set the timestamp (via rpc or at genesis config, to future or past). For the genesis config we can make use of #293 I think.

[alindima]

Moreover, we need to use the state injector for the timestamp so that we can go back in time

Do you mean for the Now storage item? I think the Now storage item would need to be modified whenever we want to set the timestamp (via rpc or at genesis config, to future or past). For the genesis config we can make use of #293 I think.

Yes. I mean that in order for the inherent data to be able to set a timestamp in the past (coming from the RPCs), we can use the state injector to set a timetamp prior to the timestamp that we want to set with the inherent. This way, the on chain inherent data validation will pass.

Indeed for genesis config, let's use #293