feat: enhance _accountKey function to handle AUTH_MODE_EXTENSION case

[YukiTsuchida]

• Issue: _sign() fails during extSignTx.
• Cause: A bug caused distinct hash values to be generated for two Account.Data instances that should be treated as identical. This has been fixed.

{
  "Id": "AHMVQM1gYJkda5xXzilZmNm8L6s=",
  "AuthType": {
    "Mode": 3,
    "Option": {
      "TypeUrl": "/verifier.sample.extension",
      "Value": ""
    }
  }
}

{
  "Id": "AHMVQM1gYJkda5xXzilZmNm8L6s=",
  "AuthType": {
    "Mode": 3,
    "Option": {
      "TypeUrl": "/verifier.sample.extension",
      "Value": "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAEDCUmZoBBegKy+RoE0WqlxsOxiRVr+pMkiz8ZhTeZjdUQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABBMKEs65z9pO27V0xKSJtC7fZApRXsLaWjZCJcoLBvf3JidQvNxtifN7FKFFeiocKtOsTXVvgm1qwRLUst0CGrlhwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
    }
  }
}

[github-actions]

LCOV of commit 987bd8f during Coverage Report #229

Summary coverage rate:
  lines......: 97.5% (585 of 600 lines)
  functions..: 95.3% (101 of 106 functions)
  branches...: no data found

Files changed coverage rate:
                                         |Lines       |Functions  |Branches    
  Filename                               |Rate     Num|Rate    Num|Rate     Num
  =============================================================================
  src/core/TxAuthManager.sol             |17.1%     82| 0.0%    14|    -      0

Full coverage report

[mattsu6666]

LGTM👍