feat: add eip712 typedDataSigner for ethr

[fermentfan]

Added the _signTypedData to the KMS eth signer to allow EIP712 signing to work.

https://docs.ethers.io/v5/api/signer/#Signer-signTypedData
https://eips.ethereum.org/EIPS/eip-712

[mirceanis]

This looks good. Thanks for adding this!

Can you try to rebase your PR on the latest next branch so the tests can run?

[fermentfan]

Should be up to date now. Just had to remove some dependabot commit so the merge request looks clean.

[codecov]

Codecov Report

Merging #1026 (1c94e3d) into next (125bf42) will increase coverage by 0.50%.
The diff coverage is 82.20%.

❗ Current head 1c94e3d differs from pull request most recent head c0e59f1. Consider uploading reports for the commit c0e59f1 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #1026      +/-   ##
==========================================
+ Coverage   80.25%   80.75%   +0.50%     
==========================================
  Files         118      124       +6     
  Lines        4056     4454     +398     
  Branches      875      950      +75     
==========================================
+ Hits         3255     3597     +342     
- Misses        798      854      +56     
  Partials        3        3