Add db.client.operation.duration metric

[alanwest]

Fixes #512

Changes

Adds a new db.client.operation.duration metric with the following attributes:

• db.system
• db.collection.name
• db.name
• db.operation.name
• db.instance.id
• network.peer.address
• network.peer.port
• server.address
• server.port

The metric is a histogram with the following default explicit bucket boundaries (see #735 (comment)): [ 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10 ]

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• [ ] schema-next.yaml updated with changes to existing conventions.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[trask]

@alanwest can you rebase now that #910 has been merged?