Add support for metrics in containers and jobs (#830)

[g-linville]

for #830

Depends on acorn-io/aml#7

Unfortunately this change updated a ridiculous number of test files.

This new feature allows users to specify metrics inside the Acornfile like this:

containers: "mycontainer": {
  image: "myimage"
  metrics: {
    port: 8081
    path: "/metrics"
  }
  ports: ["8080/http", "8081/http"]
}

Acorn runtime will create prometheus.io/{scrape,port,path} annotations on the resulting pods.

Checklist

• The title of this PR would make a good line in Acorn's Release Note's Changelog
• The title of this PR ends with a link to the main issue being address in parentheses, like: This is a title (#1216). Here's an example
• All relevant issues are referenced in the PR description. NOTE: don't use GitHub keywords that auto-close issues
• Commits follow contributing guidance
• Automated tests added to cover the changes. If tests couldn't be added, an explanation is provided in the Verification and Testing section
• Changes to user-facing functionality, API, CLI, and upgrade impacts are clearly called out in PR description
• PR has at least two approvals before merging (or a reasonable exception, like it's just a docs change)

[njhale]

Looks good!

Just one line of questions for you @g-linville

[njhale]

lgtm (pending rebase)

[tylerslaton]

How are you enforcing this? AML?

[g-linville]

Yep. The AML scheme will not allow users to specify metrics in a sidecar. It has to be done at the container level.

If the metrics are available from the sidecar, it will still work as long as the port that they specify for the metrics is one that the sidecar is using.

[tylerslaton]

Nice! Sounds good to me.