AMP4Email: Invalidate amp-lightbox and amp-image-lightbox

amp-lightbox and amp-image-lightbox don't make much sense because they occupy the full height of the document (email) and don't change their appearance based on the vertical size of the outer page nor the scroll position of the outer page.

https://github.com/ampproject/amphtml/issues/22297 is one example of this.

We have come up with no good solutions to this problem and so Gmail thinks we should disable these two components because there's no good way to use them at the moment.

Start by locating the AMP4Email handling for amp-lightbox and amp-image-lightbox, then review issue #22297 for the reported behavior. Determine how these two components should be invalidated in AMP4Email and identify the relevant tests; done means both are disabled there without changing their behavior in other contexts.

Written by the indexing model from the issue text.