Allow converters to specify a rule as being off

[JoshuaKGoldberg]

🚀 Feature Request

To unblock #1009 (review), we'll want converters to be able to output a rule setting like:

{
  ruleName: "some-rule",
  ruleSeverity: "off"
}

Existing Behavior

I don't think this is supported yet.

Change Proposal

Add to the ConvertedRuleChanges type within the return type of RuleConverters so that it can include ruleSeverity.