Wrap all amp component checks in an amp namespace check
Wrap all amp component checks in an amp namespace check

Comparison: https://blackfire.io/profiles/compare/8e0f9448-85f5-4f3d-b170-fa8fd6da1c35/graph

This saves 26590 calls to `substr()` on my empty front page.

ampproject/amp-toolbox-php,ampproject/amp-toolbox-php