[cluster-agent] Fix CWS Instrumentation metrics

[Gui774ume]

What does this PR do?

This PR fixes the metrics generated for CWS Instrumentation. Instead of using a counter that will grow forever, a distribution will better fit our monitoring use case.

Motivation

This fixes our visibility on the kubectl cp instrumentation feature added in this PR.

[agent-platform-auto-pr]

[Fast Unit Tests Report]

On pipeline 33786799 (CI Visibility). The following jobs did not run any unit tests:

Jobs:

• tests_flavor_dogstatsd_deb-x64
• tests_flavor_heroku_deb-x64
• tests_flavor_iot_deb-x64

If you modified Go files and expected unit tests to run in these jobs, please double check the job logs. If you think tests should have been executed reach out to #agent-developer-experience

[Gui774ume]

/merge

[dd-devflow]

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[pr-commenter]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv create-vm --pipeline-id=33786799 --os-family=ubuntu

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

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Use /merge -c to cancel this operation!