Add Index metrics to python sdk

[bambriz]

This PR adds Index Metrics to Python SDK.

You can capture index metrics by passing in the populate_index_metrics keyword in query items.
query_items = container.query_items(query="Select * from c", populate_index_metrics=True)

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

azure-cosmos

[simorenoh]

small suggestions but great stuff nonetheless, thank you Bryan! 👍

let's make sure to include the CHANGELOG like you said as well

[simorenoh]

also side random question, but from what I saw we send "x-ms-cosmos-populateindexmetrics" and the service returns "x-ms-cosmos-index-utilization" - is that right? there's no other additional headers that get returned on this right?

[bambriz]

also side random question, but from what I saw we send "x-ms-cosmos-populateindexmetrics" and the service returns "x-ms-cosmos-index-utilization" - is that right? there's no other additional headers that get returned on this right?

That is correct.

[bambriz]

/azp run python - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[bambriz]

/azp run python - cosmos - tests

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[simorenoh]

LGTM thanks Bryan!

[kushagraThapar]

LGTM, thanks @bambriz !