[Breaking change] Remove createFix, and just use the Replacement(s) as the fix. (Minimal change)

[andy-hanson]

PR checklist

• Addresses an existing issue: #0000
• New feature, bugfix, or enhancement
  • Includes tests
• Documentation update

Overview of change:

This is #2356, but made to have fewer changes to rule style.

CHANGELOG.md entry:

[api] Remove createFix. Replacements should be passed directly into addFailure.

[ajafff]

LGTM

this really doesn't change the formatted output? I don't get how that works without changing the relevant code. Anyways, I'm ok with it if it just works

[adidahiya]

sorry, this has conflicts now (likely because of #2359)

[andy-hanson]

Turning tests on (#2406) revealed that it did change the output of the JSON formatter. But that should be fine, right?

[ajafff]

We should at least mention the changed (JSON) formatted output in the change log. It's hard to guess for embedders to guess the new format.
My suggestion:
[formatter-change] the `fix` property in `json` output now contains either one replacement or an array of replacements