This PR introduces the necessary changes to pallet-revive for
integrating with our Ethereum JSON-RPC.
The RPC proxy itself will be added in a follow up.

## Changes

- A new pallet::call `Call::eth_transact`. This is used as a wrapper to
accept unsigned Ethereum transaction, valid call will be routed to
`Call::call` or `Call::instantiate_with_code`

- A custom UncheckedExtrinsic struct, that wraps the generic one usually
and add the ability to check eth_transact calls sent from an Ethereum
JSON-RPC proxy.
- Generated types and traits to support implementing a JSON-RPC Ethereum
proxy.

## Flow Overview:
- A user submits a transaction via MetaMask or another
Ethereum-compatible wallet.
- The proxy dry run the transaction and add metadata to the call (gas
limit in Weight, storage deposit limit, and length of bytecode and
constructor input for contract instantiation)
- The raw transaction, along with the additional metadata, is submitted
to the node as an unsigned extrinsic.
- On the runtime, our custom UncheckedExtrinsic define a custom
Checkable implementation that converts the unsigned extrinsics into
checked one
 - It recovers the signer
- validates the payload, and injects signed extensions, allowing the
system to increment the nonce and charge the appropriate fees.
- re-route the call to pallet-revive::Call::call or
pallet-revive::Call::instantiateWithCode

## Dependencies

- https://github.com/koute/polkavm/pull/188

## Follow up PRs
- #5926  
- #6147 (previously #5953)
- #5502

---------

Co-authored-by: Alexander Theißen <alex.theissen@me.com>
Co-authored-by: Cyrill Leutwiler <cyrill@parity.io>