Summary

Closes #162849

Added option to request agent diagnostics with CPU metrics. This is a new checkbox in Request diagnostics modal. When clicked, the action will contain a additional_metrics: ["CPU"].
Also replaced the click handler of Request diagnotics .zip button in Agent Details / Diagnostics tab, to open the same modal instead of immediately triggering the action.

To verify:

• Enroll 2 agents with version 8.14-SNAPSHOT
• Click on Agent diagnostics action in Agent list / Agent details
• Verify that the CPU checkbox appears in the modal window
• Verify that the diagnotics zip contains cpu.pprof file
• Verify the same in bulk request diagnostics action when selecting 2 agents

Action created in .fleet-actions:

      {
        "_index": ".fleet-actions-7",
        "_id": "224e484f-fc49-4fba-989e-8ac30db29eff",
        "_score": 1,
        "_source": {
          "@timestamp": "2024-04-02T12:24:49.062Z",
          "expiration": "2024-04-02T12:27:49.062Z",
          "agents": [
            "b4a5d936-265c-40b1-be6a-d13ca91bed36"
          ],
          "action_id": "1fc01f99-c511-49bf-9350-96ddf537b562",
          "data": {
            "additional_metrics": [
              "CPU"
            ]
          },
          "type": "REQUEST_DIAGNOSTICS",
          "traceparent": "00-a5e3c645397964952efbeceed896e9db-03730cd3f6d60955-01"
        }
      },

Checklist

Delete any items that are not applicable to this PR.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Unit or functional tests were updated or added to match the most common scenarios