fix(coil-extension): reduce code injections to 1

[sublimator]

Related to #1248

We may end up moving to emitting events on window directly, but even in that case, we'll need to provide support for old sites, along with deprecation warnings, so there is some value in reducing the amount of injections.

[wmurphyrd]

If you were to wrap that script injection in a try/catch, I think it would it be now possible to have full functioning under CSP without the script-src directives by simply running that short document.monetization polyfill script from the main paige

[sublimator]

@wmurphyrd Thanks for your input!

Yeah, I was pondering the same thing actually.
It's potentially more maintainable that way too.