feat(coderd): add times_used to coder_apps in insights API (#13292)

For now, only applied to `coder_app`s, same logic can be implemented for
VS Code, SSH, etc.

Part of #13099

coderd/apidoc/docs.go

@@ -11372,6 +11372,10 @@ const docTemplate = `{
                         "format": "uuid"
                     }
                 },
+                "times_used": {
+                    "type": "integer",
+                    "example": 2
+                },
                 "type": {
                     "allOf": [
                         {