Add queue.incoming_pods metric

[arapulido]

What does this PR do?

This PR adds the queue.incoming_pods metric

Motivation

The scheduler_queue_incoming_pods metric was added in Kubernetes 1.17, but was never added to the integration.

https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.17.md#scheduling-1

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #12674 (7c037b7) into master (5c57a8c) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Flag	Coverage Δ
kube_scheduler	97.10% <100.00%> (+0.09%)	⬆️

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