Improve a few E2E test cases

[eason9487]

Changes proposed in this Pull Request:

This PR improves a few E2E test cases:

• Fix the flaky E2E test which asserts the auto-creation of Google Ads and Merchant Center accounts.
  • It fails randomly and can usually pass after the first retry, but still often brings unwanted noise.
  • 
  • Reference: https://github.com/woocommerce/google-listings-and-ads/actions/runs/12741983827/job/35509408880#step:10:89
• Speed up the E2E test which asserts the ad billing status change.
  • Will reduce execution time from about 26 seconds to less than 1 second.
  • Before
    
  • After
    
• Remove the timeout options that are no longer needed from E2E testing.

💡 I will be skipping code review since this PR only includes developer-facing only change.

Detailed test instructions:

Confirm E2E tests can pass: https://github.com/woocommerce/google-listings-and-ads/actions/runs/12804583366

Changelog entry

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.7%. Comparing base (f25f66c) to head (a3a0a7a).
Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff              @@
##             develop   #2769      +/-   ##
============================================
- Coverage       67.1%   66.7%    -0.4%     
============================================
  Files            796     316     -480     
  Lines          24493    4922   -19571     
  Branches        1204    1204              
============================================
- Hits           16441    3282   -13159     
+ Misses          7915    1503    -6412     
  Partials         137     137              

Flag	Coverage Δ
js-unit-tests	66.7% <ø> (ø)
php-unit-tests	?

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