Remove RenderThemeCocoa::paintApplePayButton() and add a ControlPart for the ApplePayButton on iOS so it can be drawn by ApplePayButtonCocoa::draw().
This is a follow up of bug 251416.
See https://github.com/WebKit/WebKit/pull/9364#issuecomment-1410895089.
<rdar://problem/105020333>
Pull request: https://github.com/WebKit/WebKit/pull/9628
Committed 259878@main (9bc94b5f4fb6): <https://commits.webkit.org/259878@main> Reviewed commits have been landed. Closing PR #9628 and removing active labels.