[v9.2.x] UsageInsights: Record events for Explore queries (#59992)

* UsageInsights: Record events for Explore queries (#59931)

* usageinsights: record events for Explore queries

* usageinsights: make the source field optional

It is not logical to have it for an event like the dashboard-view

* usageinsights: add comment to Explore test

Explain why we are reversing a previous decision

(cherry picked from commit 74167b4d44)

* usageinsights: fix merge conflict

* Empty-Commit to trigger build

* usageinsights: fix broken tests after merge

docs/sources/setup-grafana/configure-security/export-logs.md

@@ -44,6 +44,7 @@ Logs of usage insights contain the following fields, where the fields followed b
 | `panelName` | string | Name of the panel of the query. |
 | `error` | string | Error returned by the query. |
 | `duration` | number | Duration of the query. |
+| `source` | string | Source of the query. For example, `dashboard` or `explore`. |
 | `orgId`\* | number | ID of the user’s organization. |
 | `orgName`\* | string | Name of the user’s organization. |
 | `timestamp`\* | string | The date and time that the request was made, in Coordinated Universal Time (UTC) in [RFC3339](https://tools.ietf.org/html/rfc3339#section-5.6) format. |