Replace ethereumjs usages with micro-eth-signer

[kanej]

Replace ethereumjs usages with micro-eth-signer for Hardhat v3.

With EDR replacing the Hardhat Network with a rust implementation we are using Ethereumjs less. We suspect our remaining usages are related to signing. This task is to replace those usages.

We intend to use micro-eth-signer as it is small and focused with 3 deps.

TODO

• [ ] A quick analysis of ethereumjs usages across the HHv3 codebase, identifying those usages that can be replaced with the micro-eth-signer and which can't (creating a follow up issue for those cases)
• [ ] Swap in the micro-eth-signer for these cases

[kanej]

Questions

1. Is the intent to replace actual usages in v3 with the signer, or provide a utils option that can be used in the future
2. Are there existing utils that could leverage signer instead of ethereum/js