Send plugin analytics with API key authentication (#33040)

## What changed

Allow API key sessions to send plugin-attributed `codex_plugin_used`,
`skill_invocation`, and `codex_mcp_tool_call_event` events. Continue to drop
events without a plugin ID and all other analytics events for these sessions.

## Testing

Add coverage that mixes plugin and non-plugin events and verifies that only the
three plugin-attributed event types are delivered without server-owned auth
fields.

GitOrigin-RevId: 1f47af5e9516723154f566ad032dba3ebd98abf9

codex-rs/analytics/src/events.rs

@@ -95,6 +95,15 @@ impl TrackEventRequest {
     pub(crate) fn should_send_in_isolated_request(&self) -> bool {
         matches!(self, Self::AcceptedLineFingerprints(_))
     }
+
+    pub(crate) fn can_send_with_api_key_auth(&self) -> bool {
+        match self {
+            Self::PluginUsed(event) => event.event_params.plugin.plugin_id.is_some(),
+            Self::SkillInvocation(event) => event.event_params.plugin_id.is_some(),
+            Self::McpToolCall(event) => event.event_params.plugin_id.is_some(),
+            _ => false,
+        }
+    }
 }
 
 #[derive(Serialize)]