Replace some common index based for loops with for-of loops

Replaces many loops of the form:

```js
for (let i = 0; i < elements.length; ++i) {
    const i = elements[i];
   ...
}
```

with:

```js
for (const element of elements) {
    ...
}
```

Mix of a horrible regex based find/replace and manual touch ups

extensions/merge-conflict/src/commandHandler.ts

@@ -237,9 +237,9 @@ export default class CommandHandler implements vscode.Disposable {
 			return null;
 		}
 
-		for (let i = 0; i < conflicts.length; i++) {
-			if (conflicts[i].range.contains(editor.selection.active)) {
-				return conflicts[i];
+		for (const conflict of conflicts) {
+			if (conflict.range.contains(editor.selection.active)) {
+				return conflict;
 			}
 		}