Migrate ComplexTextControllerCoreText to use SPI instead of WKSI

Migrate ComplexTextControllerCoreText to use SPI instead of WKSI
https://bugs.webkit.org/show_bug.cgi?id=138228

Reviewed by Simon Fraser.

No new tests because there is no behavior change.

* WebCore.xcodeproj/project.pbxproj:
* platform/graphics/mac/ComplexTextControllerCoreText.mm:
(WebCore::ComplexTextController::ComplexTextRun::ComplexTextRun):
(WebCore::ComplexTextController::collectComplexTextRunsForCharacters):
* platform/spi/cocoa/CoreTextSPI.h: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@175379 268f45cc-cd09-0410-ab3c-d52691b4dbfc