Closes #6901: LRC style is not added to used CSS when enable RUCSS

[Miraeld]

Description

When enabling RUCSS while LRC is already created, the used CSS does not contain the LRC CSS.

Fixes #6901
This code adds an ID Attribute to the <style> tag generated by LRC so the used CSS feature will contain the LRC css.

Type of change

• New feature (non-breaking change which adds functionality).
• Bug fix (non-breaking change which fixes an issue).
• Enhancement (non-breaking change which improves an existing functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as before).
• Sub-task of #(issue number)
• Release

Detailed scenario

Steps to reproduce the behavior:

1. Visit a page => LRC added to DB
2. Clear cache and revisit the page => LRC style added to the page
3. Enable RUCSS
4. revisit the page and wait till the used CSS is created then revisit the page => LRC style is not in the source

[data-wpr-lazyrender] {
content-visibility: auto;
} 

Technical description

Documentation

This code adds an ID Attribute to the <style> tag generated by LRC so the used CSS feature will contain the LRC css.

New dependencies

Risks

Mandatory Checklist

Code validation

• I validated all the Acceptance Criteria. If possible, provide screenshots 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 a self-explanatory code about what it does.
• I protected entry points against unexpected inputs.
• I did not introduce unnecessary complexity.
• Output messages (errors, notices, logs) are explicit enough for users to understand the issue and are actionnable.

Additional Checks

• In the case of complex code, I wrote comments to explain it.
• When possible, I prepared ways to observe the implemented system (logs, data, etc.).
• I added error handling logic when using functions that could throw errors (HTTP/API request, filesystem, etc.)

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.00% (target: -0.10%)	❌ 0.00% (target: 50.00%)

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (fb50ef3)	37955	9516	25.07%
Head commit (d17db72)	37955 (+0)	9516 (+0)	25.07% (+0.00%)

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 (#6912)	1	0	0.00%

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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[Miraeld]

While doing the scenario, we can see the new id attribute added to the <style> element.