EVM runtime: Implement value transfers

[karim-agha]

Sending tokens between two accounts without invoking any contract. This should be all implemented on the bridge level.

[raulk]

Do we want to model intra-EVM and cross runtime value transfers differently?

[karim-agha]

In this iteration we're using the bridge as the source of truth about EVM accounts balances, so it needs to go through the bridge to map EVM addresses to FIL addresses (if they exist). Also sending to an EVM account that doesn't have a FIL mapped account will trap the funds on the bridge until the mapping is discovered.

[maciejwitowski]

@raulk Do we need this for M2.1?

[Stebalien]

This was from the days of bridges. f4 makes this moot.