telemetry(amazonq): active user metric (#1063)

## Problem
- need active user metric

## Solution
- emit new metric for active user

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## License

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Author: chungjac

telemetry/definitions/commonDefinitions.json

@@ -2326,6 +2326,18 @@
                 }
             ]
         },
+        {
+            "name": "amazonq_activeUser",
+            "description": "An active user is when the user sends a message, and the user will be considered active until the remainder of the time window",
+            "metadata": [
+                {
+                    "type": "credentialStartUrl"
+                },
+                {
+                    "type": "result"
+                }
+            ]
+        },
         {
             "name": "amazonq_addMessage",
             "description": "When a message is added to the conversation",