[Impeller] give geometry classes similar API as entity / implement strokepathgeom

[jonahwilliams]

While working on making a StrokePathGeometry, I found that I needed to update the API again to provide more data for the smoothing approximation: https://github.com/flutter/engine/blob/main/impeller/entity/contents/solid_stroke_contents.cc#L213

Rather than pass through each object we need one at a time, lets just pass the same context that the Entity::Render method gets, at least for now.

[flutter-dashboard[bot]]

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[jonahwilliams]

Converting to a draft for now, I pushed up what the changes would look like with (most of) SolidStrokeGeometry implemented

[jonahwilliams]

I've verified everything is working correctly on those tests and updated to ToT. Going to land this now so we can close out this refactor. If anyone notices a problem with strokes though, this PR is the culprit 😆