Scrapers Support Multiple Metrics

[jonwinton]

Description

As discussed in the issue, there is case for a Scraper supporting multiple timeseries from a single scrape function. This PR aims to add that functionality.

The approach taken is to add a map of Metric structs to the Scraper so that each individual timeseries has an alias on the Scraper. This then translates into Scraper Functions returning a map of ScraperResult structs, with each key of the returned map matching the alias of the Metric on the Scraper.

This is a large refactor, and thus changes a lot of things: docs, tests, and each individual scraper. Because of that, the PR includes the following:

• Update the scraper docs to match the new structure
• Consolidate scrapers which collect the same type of metric.
  • iam-quota and iam-resource-usage are consolidated
  • vpc-info and subnet-available-ips are consolidated
• The Collector has to update to know to iterated through the Metrics property on a Scraper
• The commands to list the scrapers need to update to look into Metrics
• Metric docs are updated with the new metrics that are now exported

Link To Issue

Closes issue #1

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Because the API is not yet stable, I'm marking this as a new feature.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[bakayolo]

LGTM