Improve Accessibility and Functionality

[murshed]

Summary

Addresses accessibility and security improvements across Performance Lab plugins.

This PR improves screen reader accessibility on the Performance Lab admin screen (WCAG 2.4.4 Link Purpose) by providing contextual aria-label attributes for action links and buttons. It also enforces security best practices by adding rel="noopener" to external links opening in new tabs (target="_blank").

Relevant technical choices

• Accessible Action Links & Buttons (performance-lab): Added descriptive aria-label attributes to plugin card actions in perflab_render_plugin_card() (e.g., Activate {Plugin Name}, Settings for {Plugin Name}, {Plugin Name} is active) so screen reader users hear contextual labels instead of repetitive link text.
• External Link Security (target="_blank" rel="noopener"): Added rel="noopener" to all external links opening in a new tab across performance-lab, speculation-rules, embed-optimizer, optimization-detective, and site-health audit helpers to prevent reverse-tabnabbing security risks.
• Sanitization Array Updates: Updated wp_kses() allowed attributes arrays (such as in speculation-rules/settings.php) to permit 'rel' => array() on anchor tags.

[github-actions]

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Co-authored-by: murshed <fahimmurshed@git.wordpress.org>
Co-authored-by: mukeshpanchal27 <mukesh27@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 30.43478% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.30%. Comparing base (0a51c32) to head (bbf4b80).
⚠️ Report is 3 commits behind head on trunk.

Files with missing lines	Patch %	Lines
plugins/performance-lab/includes/admin/plugins.php	0.00%	14 Missing ⚠️
plugins/embed-optimizer/helper.php	0.00%	1 Missing ⚠️
...e-lab/includes/site-health/webp-support/helper.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #2598      +/-   ##
==========================================
- Coverage   70.35%   70.30%   -0.06%     
==========================================
  Files          91       91              
  Lines        7867     7876       +9     
==========================================
+ Hits         5535     5537       +2     
- Misses       2332     2339       +7     

Flag	Coverage Δ
multisite	70.30% <30.43%> (-0.06%)	⬇️
single	35.15% <26.08%> (-0.02%)	⬇️

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[mukeshpanchal27]

Thanks @murshed for the PR!

The changes look solid to me.