Add WP-CLI commands for managing AMP settings

[westonruter]

Feature description

As demonstrated by #5782, there is a need for WP-CLI commands to manipulate the AMP settings, including:

• Setting the template mode.
• Setting the Reader theme.
• Toggling mobile redirection.
• Updating the supported post types (see How to disable AMP for custom post types in a multisite network ? #5782 (comment)).
• Toggling whether all templates are supported, and otherwise toggling individual templates.
• Updating suppressed plugins
• Setting the Paired URL structure (as of Add customization of Paired AMP URLs #5558)

I'm specifically not including the manipulation of Analytics here, as we want to discourage it from being used.

In addition to updating the settings, we also need to be able to query the existing settings.

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Acceptance criteria

Implementation brief

QA testing instructions

Demo

Changelog entry