Coverage: try/catch/finally completion values. Fixes gh-1742

[rwaldron]

No description provided.

[rwaldron]

@syg heads up for failures in V8—these might be unexpected.

[leobalter]

[leobalter]

@rwaldron After battle testing this PR, I took the liberty to fix the eval tests and add some others involving return completions.

There is still a chance to add tests for try-catch-finally messing up returns using break or continue, lol.

function fn() {
  do {
    try {
      return 'NOT ME';
    } catch {}
    finally {
      break;
    }
  } while (false);
  return 42;
}

fn(); // 42;

[rwaldron]

@bakkot nice catch!