Change @typescript-eslint/return-await to level error with 'always' config

[swarmiakimmo]

Here's the documentation for "always" setting. This change will affect our codebases largely, but fortunately it is auto-fixable. The change aims to improve two scenarios:

1. Prevent easy-to-miss bugs with async / await in try-catch blocks. This issue describes the bug best:
   • Feature request - rule for await in async try catch return typescript-eslint/typescript-eslint#994
2. Improve async stack traces. The improvement is only (afaik) applicable to V8 engine, which node uses. More from this below.

The community seems to be divided on the topic. Here's a few opposing opinions about why one should not use return await convention:

• disable 'no-return-await' rule airbnb/javascript#2437
• Remove no-return-await rule eslint/eslint#12246 (comment)

My personal take on this is that better stack traces overcomes the tradeoffs, assuming we are talking about backend node processes. This PR introduces the options only in node projects just to be safe. I checked that our frontend repo had only a single place where this config change fixed something, so enabling it there too wouldn't change much either.

Want to see the stack trace improvements in practice? Just save this test.js and run node test.js to see the effect.

(function () {
  async function foo() {
    return await bar();
  }

  async function foo2() {
    return bar();
  }

  async function bar() {
    await Promise.resolve();
    throw new Error('BEEP BEEP');
  }

  foo().catch(error => console.log(error.stack));
  foo2().catch(error => console.log(error.stack));
})()

The result is that return await bar() has a better stack trace:

➜  ~ node code/rapu/test.js
Error: BEEP BEEP
    at bar (/Users/kimmo/code/rapu/test.js:14:11)
    at async foo (/Users/kimmo/code/rapu/test.js:4:12)
Error: BEEP BEEP
    at bar (/Users/kimmo/code/rapu/test.js:14:11)

For the curious, here's detailed explanation of why this happens in V8 nodejs/node#36126 (comment) and https://v8.dev/blog/fast-async