ASSETS-12635: Add cgroupV2 support

[nwoodard-cs]

Description

Add support for reading metrics from cgroupv2 (the new Ethos default), with automatic fallback to cgroupv1.

Similar change was made at https://github.com/adobe/asset-compute-pipeline/pull/98

Related Issue

Partial fix for https://jira.corp.adobe.com/browse/ASSETS-12635

Motivation and Context

Ethos containers are using cgroupv2 by default, which node-cgroup-metrics does not currently support.

How Has This Been Tested?

Tests have been added in metrics.test.js Manual tests have been performed by using nui app deploy.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] I have signed the Adobe Open Source CLA.
• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [x] I have added tests to cover my changes.
• [ ] All new and existing tests passed.