fix: releaseConnection types and promise

[wellwelwel]

This fixes the #1761 and #1563.

---

JS

The promise.js didn't have the method releaseConnection.

Instead of creating from scratch, I just "extended" it from the release method:

releaseConnection(connection) {
  if (connection instanceof PromisePoolConnection) connection.release();
}

Then, I added the test to test/integration/promise-wrappers/test-promise-wrappers.js.

---

TS

I had to fix a few wrong types before to fix the releaseConnection.

Before this PR, according by typings, this should be possible:

await (await (await pool.getConnection()).getConnection()).getConnection();
// To infinity and beyond... 😵‍💫

So, I fixed it to only Pool have the method getConnection.

• At this time, I added "negative" tests in tsc-build to ensure that the above code doesn't occur again.

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Lastly, I added some tests for each method that I changed something in types:

• releaseConnection
• release
• getConnection
• connection