Add kubernetes_agent_k8s_api_proxy_request to usage ping

What does this MR do?

Add kubernetes_agent_k8s_api_proxy_request to usage ping

The value is stored in a redis counter, which is incremented by an additional parameter in the /kubernetes/usage_metrics internal API endpoint.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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• Documentation (if required)
• Code review guidelines
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• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Related to #327414 (closed)