Use IFRAME to display HTML responses for REST API storage request failures in Site Health test

[SohamPatel46]

Summary

Fixes #1828

Relevant technical choices

• If the raw response for Optimization Detective storage request failure has a text/html type, use an IFRAME combined with sandbox and seamless attributes.
• Replace the wrapper functionwp_admin_notice with wp_get_admin_notice to whitelist the used IFRAME and posts parameters using wp_kses function.

Screenshots or screencast

[github-actions]

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Co-authored-by: SohamPatel46 <sohampate1@git.wordpress.org>
Co-authored-by: westonruter <westonruter@git.wordpress.org>

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.30%. Comparing base (68c6deb) to head (c748645).
Report is 28 commits behind head on trunk.

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk    #1849      +/-   ##
==========================================
+ Coverage   65.97%   66.30%   +0.33%     
==========================================
  Files          88       88              
  Lines        6895     6963      +68     
==========================================
+ Hits         4549     4617      +68     
  Misses       2346     2346              

Flag	Coverage Δ
multisite	66.30% <100.00%> (+0.33%)	⬆️
single	37.55% <9.52%> (-0.62%)	⬇️

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[westonruter]

This will account for headers values like text/html; charset=utf-8 and application/xml+xhtml:

Suggested change

	if ( isset( $header ) && 'text/html' === $header ) {
	if ( is_string( $header ) && str_contains( $header, 'html' ) {

[westonruter]

Aside: $header will always be set and never be null so the use of isset() probably was unnecessary, right?

[westonruter]

I found the size of the IFRAME was a bit small:

So in 6685c7a I increased the size:

[westonruter]

Looks good!