Make engine reconnection test pass every time (#3066)

* Ensure that isFreezeFrame is reset by isFirstRender, because it can't be a freeze frame if it's the first render

* `restart`-type engine starts should count as first renders

* Ensure we don't see a loading spinner after network is reconnected in test

* Make `waitForPageLoad` robust against if the page has already loaded
and make it actually wait for the Start Sketch button to be enabled

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Co-authored-by: 49fl <ircsurfer33@gmail.com>

src/components/Stream.tsx

@@ -157,6 +157,7 @@ export const Stream = () => {
   useEffect(() => {
     setIsFirstRender(kclManager.isFirstRender)
     if (!kclManager.isFirstRender) videoRef.current?.play()
+    setIsFreezeFrame(!kclManager.isFirstRender)
   }, [kclManager.isFirstRender])
 
   useEffect(() => {