implementation of abi::decode_packed

[noot]

Is your feature request related to a problem? Please describe.
It would be nice to have a decoding counterpart to solidity abi.encodePacked implemented. afaik this is not implemented, only non-packed decoding is: https://docs.rs/ethers/latest/ethers/abi/index.html#functions This is needed for decoding things encoded by solidity abi.encodePacked.

Describe the solution you'd like
An implementation of abi::decode_packed that can decode data encoded by abi::encode_packed/solidity abi.encodePacked

Describe alternatives you've considered
none

Additional context
happy to try to implement this if needed!