Refactor to remove forEachLine and getLineMetadata helpers, reimplement MD012/MD018/MD020/MD031 using micromark tokens.

test/snapshots/markdownlint-test-scenarios.js.md

@@ -35694,6 +35694,23 @@ Generated by [AVA](https://avajs.dev).
             'blanks-around-fences',
           ],
         },
+        {
+          errorContext: '```',
+          errorDetail: null,
+          errorRange: null,
+          fixInfo: {
+            insertText: `␊
+            `,
+            lineNumber: 66,
+          },
+          lineNumber: 66,
+          ruleDescription: 'Fenced code blocks should be surrounded by blank lines',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md031.md',
+          ruleNames: [
+            'MD031',
+            'blanks-around-fences',
+          ],
+        },
         {
           errorContext: 'fence {MD031:64} {MD031:65} {M...',
           errorDetail: null,
@@ -35798,7 +35815,7 @@ Generated by [AVA](https://avajs.dev).
       1. Text␊
       ␊
          \`\`\`shell␊
-         fence {MD031:64} {MD031:65} {MD032:65} {MD040:66}␊
+         fence {MD031:64} {MD031:65} {MD031:66} {MD032:65} {MD040:66}␊
       ␊
         \`\`\`␊
       `,