[Image Redux] Remove Style::Image's drawResolving family of functions

https://bugs.webkit.org/show_bug.cgi?id=326369

Reviewed by Darin Adler and Tim Nguyen.

Style::Image's drawResolving family of functions were only needed for staging. They can now be removed.

* Source/WebCore/style/values/images/kinds/StyleImage.cpp:
* Source/WebCore/style/values/images/kinds/StyleImage.h:

Canonical link: https://commits.webkit.org/322769@main