Fixes #6613 Improve LCP warmup process

[Tabrisrp]

Description

Update the LCP warmup process by:

• Doing only a request on the mobile homepage
• Reducing the delay between each URL sent to the SaaS
• Making the requests non-blocking

Fixes #6613

Type of change

• Enhancement (non-breaking change which improves an existing functionality).

Checklists

Feature validation

• I validated all the Acceptance Criteria. If possible, provide sreenshots or videos.
• I triggered all changed lines of code at least once without new errors/warnings/notices.
• I implemented built-in tests to cover the new/changed code.

Code style

• I wrote self-explanatory code about what it does.
• I wrote comments to explain why it does it.
• I named variables and functions explicitely.
• I protected entry points against unexpected inputs.
• I did not introduce unecessary complexity.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.07% (target: -0.10%)	❌ 36.36% (target: 50.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (74186d3)	37122	14325	38.59%
Head commit (118c59e)	37189 (+67)	14377 (+52)	38.66% (+0.07%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#6615)	22	8	36.36%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[jeawhanlee]

@Tabrisrp @wordpressfan This is totally out of scope for this PR but I figured since we already touched here, we might as well just do it. For easier debugging, can we add the url to the response log here:

wp-rocket/inc/Engine/Common/JobManager/APIHandler/APIClient.php

Line 103 in 6923210

'Add to queue response body',

Perhaps something like this: https://example.org/lcp-page - Add to queue response body