Reporting: Handle timeouts in rendering (#20415)

* Added timeout in grpc call to plugins for rendering

(cherry picked from commit 7a8c6a9b54)

pkg/api/render.go

@@ -40,6 +40,7 @@ func (hs *HTTPServer) RenderToPng(c *m.ReqContext) {
 		return
 	}
 
+	maxConcurrentLimitForApiCalls := 30
 	result, err := hs.RenderService.Render(c.Req.Context(), rendering.Opts{
 		Width:           width,
 		Height:          height,
@@ -50,7 +51,7 @@ func (hs *HTTPServer) RenderToPng(c *m.ReqContext) {
 		Path:            c.Params("*") + queryParams,
 		Timezone:        queryReader.Get("tz", ""),
 		Encoding:        queryReader.Get("encoding", ""),
-		ConcurrentLimit: 30,
+		ConcurrentLimit: maxConcurrentLimitForApiCalls,
 	})
 
 	if err != nil && err == rendering.ErrTimeout {