ESLint formatter returns invalid SARIF in some cases

[michaelcfanning]

Specifically, we do not always provide the rule ID, e.g.,

{
  "level": "error",
  "message": {
    "text": "Parsing error: ImportDeclaration should appear when the mode is ES6 and in the module context."
  },
  "locations": [
    {
      "physicalLocation": {
        "artifactLocation": {
          "uri": "file:///C:/Dev/SecureApp/SecureApp/ts/node_modules/esrecurse/gulpfile.babel.js",
          "index": 905
        }
      }
    }
  ]
},