CSP support for AMP pages

[Rich-Harris]

Describe the problem

We added CSP support in #3499, but it didn't apply to AMP pages.

Describe the proposed solution

I think we just have to add this monstrosity but I didn't look too closely yet

Alternatives considered

No response

Importance

nice to have

Additional Information

No response

[Rich-Harris]

This... isn't actually possible. If you follow the instructions in https://amp.dev/documentation/guides-and-tutorials/optimize-and-measure/secure-pages/, your page won't validate:

AMP is a trainwreck.