test: refactor test-debugger-remote

1. The test doesn't attach an event listener for `exit` events and
   removes them before killing. The intention is to fail the tests if
   the processes exit normally. This patch attaches the `exit` event
   handlers.

2. Replace `var`s with `let`s and `const`s.

3. Replace `==` based assertion with `strictEqual` assertion.

4. Use `common.PORT` instead of `5959`.

5. The test used to expect only one string "connecting to
   localhost:5959 ... ok", but the debugger actually emits another
   string, "break in test/fixtures/empty.js:2". This patch asserts if
   both of them are received in the same order.

Refer: https://github.com/nodejs/node/issues/10361
PR-URL: https://github.com/nodejs/node/pull/10455



Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>