[Build] Support public builds on the macOS 26 SDK

[emw-apple]

965167c

[Build] Support public builds on the macOS 26 SDK
https://bugs.webkit.org/show_bug.cgi?id=294213
rdar://152747039

Reviewed by Abrar Rahman Protyasha.

Copy SDK additions from macOS Sequoia, and fix a couple build failures
in places where code is assuming an internal SDK.

Rename the directories containing SPI modules added in
https://commits.webkit.org/293940@main. Directory names need to match
the module name imported, so that the compiler enters the directory and
discovers the modulemap.

* Source/WebKit/Platform/cocoa/WKMaterialHostingSupport.swift:
* Source/WebKit/Platform/spi/Cocoa/Modules/WritingToolsUI_Private_SPI/WritingToolsUISPI.h: Renamed from Source/WebKit/Platform/spi/Cocoa/Modules/WritingToolsUI/WritingToolsUISPI.h.
* Source/WebKit/Platform/spi/Cocoa/Modules/WritingToolsUI_Private_SPI/module.modulemap: Renamed from Source/WebKit/Platform/spi/Cocoa/Modules/WritingToolsUI/module.modulemap.
* Source/WebKit/Platform/spi/Cocoa/Modules/WritingTools_SPI/WritingToolsSPI.h: Renamed from Source/WebKit/Platform/spi/Cocoa/Modules/WritingTools/WritingToolsSPI.h.
* Source/WebKit/Platform/spi/Cocoa/Modules/WritingTools_SPI/module.modulemap: Renamed from Source/WebKit/Platform/spi/Cocoa/Modules/WritingTools/module.modulemap.
* Source/WebKit/_WebKit_SwiftUI/Implementation/WebViewRepresentable.swift:
(WebPageWebView.configureScrollInputBehavior(_:for:)):
* WebKitLibraries/SDKs/macosx26.0-additions.sdk/SDKSettings.plist: Added.
* WebKitLibraries/SDKs/macosx26.0-additions.sdk/SymlinkedHeaders-output.xcfilelist: Added.
* WebKitLibraries/SDKs/macosx26.0-additions.sdk/SymlinkedHeaders.xcfilelist: Added.
* WebKitLibraries/SDKs/macosx26.0-additions.sdk/usr/local/include/AvailabilityProhibitedInternal.h: Added.

Canonical link: https://commits.webkit.org/296023@main

c9c9977

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	⏳ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 playstation
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash c9c9977)

Details

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
🧪 style	🛠 ios	🛠 mac	🛠 wpe	⏳ 🛠 win
⏳ 🧪 bindings	⏳ 🛠 ios-sim	🛠 mac-AS-debug	🧪 wpe-wk2	⏳ 🧪 win-tests
⏳ 🧪 webkitperl	⏳ 🧪 ios-wk2	🧪 api-mac	🧪 api-wpe
⏳ 🧪 webkitpy	⏳ 🧪 ios-wk2-wpt	🧪 mac-wk1	⏳ 🛠 wpe-cairo
⏳ 🛠 🧪 jsc	⏳ 🧪 api-ios	🧪 mac-wk2	🛠 gtk
⏳ 🛠 🧪 jsc-arm64	⏳ 🛠 vision	🧪 mac-AS-debug-wk2	🧪 gtk-wk2
	🛠 vision-sim	🧪 mac-wk2-stress	🧪 api-gtk
	⏳ 🧪 vision-wk2	🧪 mac-intel-wk2	⏳ 🛠 playstation
	⏳ 🛠 tv	⏳ 🛠 mac-safer-cpp
	⏳ 🛠 tv-sim
	⏳ 🛠 watch
	🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash c9c9977)

Details

Misc	iOS, visionOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 win
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2	⏳ 🧪 win-tests
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-cairo
	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
	✅ 🛠 vision	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 vision-sim	✅ 🧪 mac-wk2-stress	✅ 🧪 api-gtk
✅ 🛠 🧪 merge	✅ 🧪 vision-wk2	✅ 🧪 mac-intel-wk2	✅ 🛠 playstation
	✅ 🛠 tv	✅ 🛠 mac-safer-cpp
	✅ 🛠 tv-sim
	✅ 🛠 watch
	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 296023@main (965167c): https://commits.webkit.org/296023@main

Reviewed commits have been landed. Closing PR #46514 and removing active labels.