[Deployment Manager] Add support for auto completion of configuration files

This is a feature request

- Cloud Code for IntelliJ version: 20.4.3
- OS: Ubuntu 18.04

**What did you do?**
I tried to create a deployment manager file from scratch using IntelliJ (version 2020.1.1 community edition) and the Cloud Code plugin (see version above).

**What did you expect to see?**
I would expect to have auto complete support while editing the file.

**What did you see instead?**
There is no auto complete at all

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As the article [Creating a Basic Configuration](https://cloud.google.com/deployment-manager/docs/configuration/create-basic-configuration) suggests, a human being should manually search for valid values using

gcloud deployment-manager types list

and check the syntax by a trial and error process.

Behind the scenes I imagine that the tool should call commands such as:

gcloud deployment-manager types list

or using information from the API reference such as [Method: networks.insert](https://cloud.google.com/compute/docs/reference/rest/v1/networks/insert) so it shouldn't be that hard.

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I originally started this question on this [Stack Overflow question](https://stackoverflow.com/questions/61594828/does-a-good-tool-exist-to-work-with-google-cloud-platform-deployment-manager-fil)