Update amp-toolbox-php to 0.6.0 (almost) and update error page to support fatal errors (in PHP 7+)

[westonruter]

Summary

• Update amp-toolbox-php to dev-main which is 0.6.0 minus Adapt PreloadHeroImages to support new OptimizeHeroImage configuration arguments amp-toolbox-php#55.
• Fix fatal error now raised in AMP_Object_Sanitizer since Tag::OBJECT no longer exists in amp-toolbox-php.
• Catch fatal errors during post-processing in PHP 7+ in the same way exceptions are caught.
• Add a link to the support forum on the error page.

Fatal Error Handling

Before	After

Forum Link

Before	After

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

[github-actions]

Plugin builds for 6387eca are ready 🛎️!

• Download development build
• Download production build

[schlessera]

Do we actually want this link to be translatable? It could potentially allow an attacker to send the user to a "fishing support forum" where they post their logs to a third-party... Yes, it is far-fetched, I know.

[westonruter]

The URL was made translatable in #6320 as well. There are these instances of translatable URLs:

includes/options/class-amp-options-manager.php
470:						esc_url( __( 'https://wordpress.org/support/article/why-should-i-use-https/', 'amp' ) )

assets/src/components/error-screen/index.js
49:						__( 'https://wordpress.org/support/plugin/amp/', 'amp' ),

assets/src/settings-page/analytics.js
26:	__( 'https://wordpress.org/plugins/google-site-kit/', 'amp' ),
27:	__( 'https://developers.google.com/analytics/devguides/collection/amp-analytics/', 'amp' ),
213:							__( 'https://amp.dev/documentation/components/amp-analytics/', 'amp' ),
215:							__( 'https://amp-wp.org/documentation/getting-started/analytics/', 'amp' ),
220:							__( 'https://amp.dev/documentation/guides-and-tutorials/optimize-and-measure/configure-analytics/analytics-vendors/', 'amp' ),

assets/src/settings-page/paired-url-structure.js
337:						__( 'https://amp-wp.org/?p=10004', 'amp' ),

src/Admin/SiteHealth.php
248:				esc_url( __( 'https://www.php.net/manual/en/book.curl.php', 'amp' ) ),

src/DevTools/ErrorPage.php
277:				esc_url( __( 'https://wordpress.org/support/plugin/amp/', 'amp' ) )

src/LoadingError.php
47:							esc_url( __( 'https://wordpress.org/support/plugin/amp/', 'amp' ) )

Granted, we aren't going to have alternative support forums so I'm fine with removing the translation in both places.

cc @delawski

[westonruter]

QA Passed

Added this code to a plugin:

add_filter( 'amp_optimizer_config', function ( $x ) {
	AMP_Template_Customizer::DOES_NOT_EXIST;
	return $x;
} );

As expected, this fatal error resulted in the error screen being shown with a link to the support forum: