Implement a simple NpmManager

[ktarasenko]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #1937

Description
Introduces a simple way to download Implementation Guides and Knowledge Artifacts from the NPM package server.

Alternative(s) considered
I spent some amount of time trying to port the NpmManager from Cqf framework to support android, but the amount of work to make the underlying HAPI machinery was more than the actual implementation of the simple NPM client.
Key difference to Cqf/Hapi solution:

• The implementation reads files one-by-one and doesn't require keeping the whole NPM package in memory
• hapi NPM client has a long tail of features to support edge cases that might or might not be necessary to communicate to the simple NPM server (searching over the package manager, intensive caching, resolving packages using external indices), For simplicity, most of them were omitted in the implementation, but might be necessary after the extensive testing

Type
Feature

Screenshots (if applicable)

Checklist

• I have read and acknowledged the Code of conduct.
• I have read the Contributing page.
• I have signed the Google Individual CLA, or I am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have run ./gradlew spotlessApply and ./gradlew spotlessCheck to check my code follows the style guide of this project.
• I have run ./gradlew check and ./gradlew connectedCheck to test my changes locally.
• I have built and run the demo app(s) to verify my change fixes the issue and/or does not break the demo app(s).

[omarismail94]

@ktarasenko can you resolve the dependency conflict and tag Jing or I when done? We can probably merge this PR!

[aditya-07]

Added a few comments.

[aditya-07]

LGTM