certain formatters return \n when there are no errors

[alan-agius4]

Bug Report

• TSLint version: 5.11.x

Actual behavior

When using the API

Ex:

const Formatter = tslint.findFormatter('prose');
const formatter = new Formatter();
const output = formatter.format(result.failures, result.fixes);

Sometimes it will return \n when no having an failures, or the failures have been fixed. This applies almost to all formatters.

See: https://github.com/palantir/tslint/blob/master/src/formatters/proseFormatter.ts#L34 and
https://github.com/palantir/tslint/blob/master/src/formatters/proseFormatter.ts#L62

Expected behavior

I'd like that this return an empty string so we can test easily for a falsy value and don't emit anything to the console.

I'll happily do a PR to fix these issues, if you agree.

[JoshuaKGoldberg]

Related: #3744, #3837.

Question before this should be considered ready for a PR: are there any uses where \n is the preferred output?

[JoshuaKGoldberg]

☠️ TSLint's time has come! ☠️

TSLint is no longer accepting most feature requests per #4534. See typescript-eslint.io for the new, shiny way to lint your TypeScript code with ESLint. ✨

It was a pleasure open sourcing with you all!

[JoshuaKGoldberg]

🤖 Beep boop! 👉 TSLint is deprecated 👈 (#4534) and you should switch to typescript-eslint! 🤖

🔒 This issue is being locked to prevent further unnecessary discussions. Thank you! 👋