[receiver/mongodb] Add integration test

[djaglowski]

The task is essentially to create an integration test that:

1. Starts an mongodb docker container
2. Initializes the mongodbreceiver component from it's factory
3. Scrapes metrics from the docker container
4. Validates that the expected metrics are scraped (using the scrapertest package)

As far as examples go, there are a few components out there that have integration tests using the same pattern.
For instance:

Mysql receiver integration test
Nginx receiver integration test

Adapted from post by @BinaryFissionGames in #10165 (comment)

[Frapschen]

I would like help it.

[djaglowski]

Thanks @Frapschen. I've assigned it to you