Touch amendment

[RichardAH]

An amendment to ensure that all accounts that are affected or could be affected by a txn appear in the txn metadata, akin to the touch command in *nix systems.

WIP

https://github.com/Xahau/xahaud/issues/288

High Level Overview of Change

Context of Change

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Tests (you added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation update
• [ ] Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• [ ] Release

API Impact

• [ ] Public API: New feature (new methods and/or new fields)
• [ ] Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• [ ] libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• [ ] Peer protocol change (must be backward compatible or bump the peer protocol version)

[dangell7]

Because the new field TouchCounter doesnt exist and is optional the first update leaves us with an empty json PreviousFields.

This occurs here. I dont believe we need do anything I just wanted to notate it.

{
    "ModifiedNode" : 
    {
        "FinalFields" : 
        {
            "Account" : "rPMh7Pi9ct699iZUTWaytJUoHcJ7cgyziK",
            "AccountIndex" : "1",
            "Balance" : "997999990",
            "Flags" : 41943040,
            "OwnerCount" : 1,
            "Sequence" : 3,
            "TouchCount" : "1"
        },
        "LedgerEntryType" : "AccountRoot",
        "LedgerIndex" : "DE3BE7FDF6864FB024807B36BFCB4607E7CDA7D4C155C7AFB4B0973D638938BF",
        "PreviousFields" : {}
    }
}

[dangell7]

For Reviewers:

When a trustline is frozen it updates the TouchCount for the account that has the trustline. This didn't occur previously.

This was one of the only locations where the number of affected nodes is tested. This change does mean that every TSH will get a TouchCount update which may add txns to their account_tx stream which they may or may not understand.