Prevent sanitization of Customizer preview styles

[pierlon]

Summary

When the site is being previewed in the Customizer:

• Adds the data-ampdevmode attribute to scripts so that they are ignored by sanitizers
• Adds the data-ampdevmode attribute to all dependencies of the customizer-preview style handle, including itself
• Removes references of the allow_dirty_styles and allow_dirty_scripts sanitizer args from the codebase as they are no longer being used anywhere

Fixes #4804.

Checklist

• My pull request is addressing an open issue (please create one otherwise).
• 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).

[pierlon]

@westonruter Do you think this PR also include the prevention of CSS tree shaking when the sanititization argument allow_dirty_styles is true?

[github-actions]

Plugin builds for 9dd7976 are ready 🛎️!

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[westonruter]

Something else we need to address is how the Customizer preview handles (or doesn't currently) the addition of a header video in Twenty Seventeen. Currently a YouTube video just fails to show up, and an MP4 is positioned in the wrong spot. We need to make sure that the header_video and external_header_video settings get a transport assigned of refresh as opposed to postMessage to deal with this. I'll address this as part of #4984.

[westonruter]

(E2E tests failing is a known issue to be fixed by #4980.)