test: no timer a popup test started fires after cleanupPopup() (closes #578)

tests/support/popupBoot.js recorded every interval the popup sets but left
timeouts alone, so the two-second timer that clears a flash message could fire
after cleanupPopup() had removed the page, throw "document is not defined",
and fail whichever test file the jest worker had moved on to. Timeouts still
run for real during a popup test; the helper now records each one until it
fires or is cleared, and cleanupPopup() clears the ones still pending. The
fake timers tests/firstWalletRefresh.test.js used to hold that timer are
removed. tests/popupBoot.test.js shows a flash message, cleans up, waits past
the flash duration, and fails if anything throws.

Model: opus-5-5

tests/firstWalletRefresh.test.js

@@ -61,16 +61,12 @@ async function importOn(page, { tab, field, secret }) {
     await page.click("btn-add-wallet-confirm");
 }
 
-// Fake timers hold the timer of the flash message an import ends with, which
-// would otherwise fire after cleanupPopup() has removed the page and throw.
 beforeEach(() => {
-    jest.useFakeTimers();
     chainBalance = "0.0";
 });
 
 afterEach(() => {
     cleanupPopup();
-    jest.useRealTimers();
 });
 
 describe("a popup that opened on Welcome", () => {