feat: add cli functionality to dataproc quickstart

[bradmiro]

I made the Dataproc quickstart runnable and provided instructions on how to run it with maven.

[kurtisvg]

We strongly prefer not to have CLI components for Java samples. The reason for this is that the vast majority of users use an IDE, and copy and paste the snippets from the doc site. They should be able to run the sample in their IDE, as they may not be comfortable with the command-line.

If you absolutely have to have interaction via command-line, you can reformat the existing no-args quickstart to a Main function and include instructions to edit the snippet to run the main class. This allows it to be run from the command-line while still preserving the ability for the function to be triggered in an IDE easily.

[bradmiro]

Given that this is an E2E tutorial, I discussed with the TW and we agreed that all of the "quickstart" samples in all languages should be runnable as-is without modifying any code (including uncommenting and setting variables). This is the only sample we intend to do this for and the rest will follow the traditional framework, such as the createCluster sample. I definitely acknowledge we're making atypical trade-offs to create this functionality.