Admin: Add search engine visibility test to Site Health

[himanshupathak95]

Trac ticket: https://core.trac.wordpress.org/ticket/63375

The "Discourage search engines" setting can be easily overlooked in the "At A Glance widget", potentially causing SEO issues during site launches. The Site Health report provides another visibility point for this critical setting.
This PR adds a new Site Health test to make site owners more aware when search engines are discouraged from indexing their sites.

Changes:

• Adds a new Site Health test under the "Privacy" category to check if search engines are discouraged
• Displays "recommended" status when search engines are discouraged, with clear messaging to review settings
• Provides a direct link to the Reading Settings page to change this option

[github-actions]

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[github-actions]

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[himanshupathak95]

This is how the changed 'info' dashicon color looks like -

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 60529
GitHub commit: 6d58651

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.