Fix Flaky PW test: Multi-currency widget setup

[jessepearson]

Fixes #10262

Changes proposed in this Pull Request

• Rename the test file to have the merchant prefix.
• Add a restoreCurrencies call before running the tests to ensure the currencies are properly set up.
• Add a more defined locator to open the widget settings sidebar.
• Use Prettier to remove unnecessary awaits.

Testing instructions

• Tests should pass in full suite, or just by the file being called.

---

• Run npm run changelog to add a changelog file, choose patch to leave it empty if the change is not significant. You can add multiple changelog files in one PR by running this command a few times.
• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

[allie500]

Thanks for working on this one! Code changes look good to me. I ran the full suite of Playwright tests and these passed. I did get two failures though.

 2 failed
    [shopper] › shopper/shopper-checkout-purchase.spec.ts:47:8 › Successful purchase › Carding protection true › using a basic card 
    [shopper] › shopper/shopper-checkout-purchase.spec.ts:58:8 › Successful purchase › Carding protection true › using a 3DS card 
  146 passed (38.7m)

Running these tests in isolation worked. All tests passed.

% npm run test:e2e-pw merchant-multi-currency-widget        

> woocommerce-payments@8.8.0 test:e2e-pw
> ./tests/e2e-pw/test-e2e-pw.sh merchant-multi-currency-widget

🎭 Running Playwright e2e tests in default headless mode, skipping @todo.

Running 6 tests using 1 worker
[setup] › auth.setup.ts:37:6 › authenticate as admin
Using existing merchant state.
[setup] › auth.setup.ts:83:6 › authenticate as customer
Using existing customer state.
  6 passed (37.1s)

I think we'll need to deal with those other two failures in a separate issue.