Revisit disabled LCP/ATF tests to fix them and re-enable them

[MathieuLamiot]

Context We recently disabled many LCP/ATF tests (see the enabled values in src/support/results/expectedResults files); this allowed to clean Rocket-E2E results but it is not viable in the mid/long run. Those tests must either be re-enabled once fixed, or deleted if irrelevant. A first investigation quickly started here

Expected behavior For each of the disabled templates, on mobile and/or desktop:

• Confirm manually with QA that, with wp-rocket develop branch, the LCP/ATF optimization is correctly applied (expected HTML modifications) on the template.
• If not, then log a GH issue and reference the template in it.
• Else, go to the wp-rocket DB and extract the LCP and viewport values for this tempalte in the mobile and/or desktop. Modify the expected results of the Rocket-E2E JSON file to match what you extracted in the DB. Then, re-run Rocket-E2E for this template and confirm it is now passing.

Additional note: We suspect some tests are failing because the template uses external images (from another host) that can sometimes be slower than the beacon execution. Several possibilities to discuss:

• Use the new filter to make the beacon execution later than normal, to avoid those cases.
• Move the images to the E2E website to avoid network issues
• Replace those templates with equivalents with images hosted on the E2E website.

Acceptance Criteria

• There are no disabled tests in LCP/ATF templates of Rocket-E2E. If there are some, they are associated to a GH issue on wp-rocket.
• Rocket-E2E is passing without errors for LCP/ATF tests.