fix: display raw key in the message

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Which language are you using?

JSON, JSON5, JSONC

What did you do?

no-duplicate-keys:

I expected fo\n\u006ft to appear in the error message, but it appears as fo(newline)ot.

sort-keys:

I expected bfo\n\u006ft and afo\n\u006ft to apper in the error message, but it appears as bfo(newline)ot and afo(newline)ot.

What did you expect to happen?

• I expected fo\n\u006ft to appear in the error message, but it appears as fo(newline)ot.
• I expected bfo\n\u006ft and afo\n\u006ft to apper in the error message, but it appears as bfo(newline)ot and afo(newline)ot.

Link to minimal reproducible Example

The following code would help identify the problem:

// eslint json/no-duplicate-keys: "error"

{
  "fo\not": 1,
  "fo\n\u006ft": 2
}

// eslint json/sort-keys: "error"

{
  "bfo\n\u006ft": 2, 
  "afo\n\u006ft": 1
}

What changes did you make? (Give an overview)

This PR was motivated by #151 (comment).

In this PR, I've updated the data property to show raw key values in messages instead of processed ones.

The no-duplicate-keys and sort-keys rules were mainly affected.

Also, I extracted the getKey and getRawKey helper functions into util.js, since they can be reused across multiple rules.

Related Issues

Ref: #151 (comment)

Is there anything you'd like reviewers to focus on?

N/A