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

---------

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

e2e/playwright/test-utils.ts

@@ -16,14 +16,14 @@ export const TEST_COLORS = {
 } as const
 
 async function waitForPageLoad(page: Page) {
-  // wait for 'Loading stream...' spinner
-  await page.getByTestId('loading-stream').waitFor()
   // wait for all spinners to be gone
-  await page
-    .getByTestId('loading')
-    .waitFor({ state: 'detached', timeout: 20_000 })
+  await expect(page.getByTestId('loading')).not.toBeAttached({
+    timeout: 20_000,
+  })
 
-  await page.getByTestId('start-sketch').waitFor()
+  await expect(page.getByTestId('start-sketch')).toBeEnabled({
+    timeout: 20_000,
+  })
 }
 
 async function removeCurrentCode(page: Page) {