fix(payment): fix GooglePay strategy spec crashing under Jest 29 / Node 22

[PavlenkoM]

What/Why?

The google-pay-integration test suite was failing on master with Jest worker encountered N child process exceptions, exceeding retry limit — unrelated to any feature work.

Root cause: the CHECKOUT-10061 toolchain upgrade (TypeScript 4.7→5.8, Jest 29 + Node 22, #3273) made the worker crash on unhandled promise rejections; Jest 26 previously tolerated them. google-pay-payment-strategy.spec.ts had two distinct problems, the first masking the second:

1. Leaked unhandled rejections from fire-and-forget click handlers. Several tests trigger an async click handler via button.click() and never await it. When the handler reports an error via onError and re-throws, the rejection is never handled → it crashes the worker. This was amplified by the button being created once in beforeAll and shared across all tests with no deinitialize in between, so click listeners accumulated and a later button.click() fired an earlier test's throwing handler. (The newer container-mode tests added in feat(payment): PI-5215 [FE][Google Pay] Implement container mode in GooglePayPaymentStrategy #3247 already avoid this by capturing and awaiting the handler.)
2. A pre-existing assertion failure masked by the crash. PI-5216 (feat(payment): PI-5216 show full list of payment methods when GooglePay direct-pay flow payment is processed #3267) mocked _completeCheckoutFlow to a no-op in the direct-pay describe, but that method is the only place LoadingHide is called on the success path — so should hide loading indicator after completing checkout could never pass.

This PR fixes the suite with test-only changes — no production code is touched:

• Create a fresh button per test (beforeAll → beforeEach, removed in afterEach) so click listeners can't accumulate across tests.
• For the two tests whose flow rejects (onError, getNonce), capture the registered click handler and await expect(...).rejects.toThrow(...) instead of fire-and-forget button.click() — matching the existing feat(payment): PI-5215 [FE][Google Pay] Implement container mode in GooglePayPaymentStrategy #3247 container-test pattern.
• For should hide loading indicator after completing checkout, restore the real _completeCheckoutFlow (jsdom only logs the unimplemented window.location.replace, it doesn't throw) so the test asserts genuine production behaviour rather than a stub.

Rollout/Rollback

No production impact — changes are limited to packages/google-pay-integration/src/google-pay-payment-strategy.spec.ts. No experiments, feature flags, or database migrations. Rollback is a straight revert of this commit.

Testing

• npx nx run google-pay-integration:test → 71 suites / 414 tests pass, run repeatedly with no flaky worker crashes (the failure was timing-sensitive).
• npx eslint packages/google-pay-integration/src/google-pay-payment-strategy.spec.ts → clean.
• Verified each change is independently necessary: with the fresh button alone, reverting onError to button.click() still crashes; the _completeCheckoutFlow test now exercises the real method (confirmed it calls LoadingHide via production code, not a stub).

Before:

After:

---

Note

Low Risk
Changes are confined to one spec file with no production code, payment runtime, or deployment impact.

Overview
Test-only updates to google-pay-payment-strategy.spec.ts so the suite stops crashing Jest workers after the Jest 29 / Node 22 upgrade (unhandled promise rejections are no longer tolerated).

Wallet button setup now uses beforeEach to create and append a fresh DOM node and afterEach to remove it, instead of a shared beforeAll button that let click listeners stack across tests.

For flows that reject (onError on widget failure, coupons path when getNonce fails), tests no longer fire button.click() without awaiting; they pull the registered click handler from addEventListener mocks and await expect(...).rejects.toThrow(...), matching the existing container-button pattern.

In the direct-pay-on-click block, should hide loading indicator after completing checkout restores the real _completeCheckoutFlow (drops the no-op spy) so LoadingHide is asserted on the actual success path instead of a stub that never hid loading.

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[PavlenkoM]

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