[threaded-animation-resolution] add support for blending opacity values

[graouts]

c31a035

[threaded-animation-resolution] add support for blending `opacity` values
https://bugs.webkit.org/show_bug.cgi?id=268738
rdar://122304627

Reviewed by Simon Fraser.

In order to add support for blending `opacity` values we make `AcceleratedEffect`
adopt the `KeyframeInterpolation::interpolateKeyframes()` method and its various
callbacks to deal with `AcceleratedEffect::Keyframe` values. We wrap this into
the new `AcceleratedEffect::apply()` method which is called from `RemoteAcceleratedEffectStack`
in the `computeValues()` method.

We compute the blended values in three different places in `RemoteAcceleratedEffectStack`.

When we resolve effects on the main thread (macOS) we have an `initEffectsFromScrollingThread()`
method to initialize the `CAPresentationModifier` objects which will apply the blended
values, and then on subsequent display updates we call `applyEffectsFromScrollingThread()`.

When we resolve effects on the scrolling thread (iOS) there is no initialization step
required and the single `applyEffectsFromScrollingThread()` method suffices.

Future patches will add support for the other transform-related and filter-related
accelerated properties.

* Source/WebCore/PAL/pal/spi/cocoa/QuartzCoreSPI.h:
* Source/WebCore/platform/animation/AcceleratedEffect.cpp:
(WebCore::blend):
(WebCore::AcceleratedEffect::apply):
* Source/WebCore/platform/animation/AcceleratedEffect.h:
* Source/WebKit/UIProcess/RemoteLayerTree/RemoteAcceleratedEffectStack.h:
* Source/WebKit/UIProcess/RemoteLayerTree/RemoteAcceleratedEffectStack.mm:
(WebKit::RemoteAcceleratedEffectStack::initEffectsFromScrollingThread):
(WebKit::RemoteAcceleratedEffectStack::applyEffectsFromScrollingThread const):
(WebKit::RemoteAcceleratedEffectStack::applyEffectsFromMainThread const):
(WebKit::RemoteAcceleratedEffectStack::computeValues const):
(WebKit::RemoteAcceleratedEffectStack::clear):

Canonical link: https://commits.webkit.org/274102@main

c01c3b4

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 gtk
	✅ 🧪 api-ios	🧪 mac-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	❌ 🧪 api-gtk
	✅ 🛠 tv-sim
	✅ 🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on previous version of this PR (hash 1f79be0)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	❌ 🛠 ios	❌ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	❌ 🛠 ios-sim	❌ 🛠 mac-AS-debug	🧪 wpe-wk2
✅ 🧪 webkitperl	❌ 🧪 ios-wk2	❌ 🧪 api-mac	✅ 🧪 api-wpe
	❌ 🧪 ios-wk2-wpt	❌ 🧪 mac-wk1	✅ 🛠 gtk
⏳ 🛠 🧪 jsc	❌ 🧪 api-ios	❌ 🧪 mac-wk2	🧪 gtk-wk2
	❌ 🛠 tv	❌ 🧪 mac-AS-debug-wk2	✅ 🧪 api-gtk
	🛠 tv-sim	❌ 🧪 mac-wk2-stress
	❌ 🛠 watch
	⏳ 🛠 watch-sim

[webkit-early-warning-system]

EWS run on current version of this PR (hash c01c3b4)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
✅ 🧪 bindings	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	✅ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 gtk
	✅ 🧪 api-ios	🧪 mac-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	❌ 🧪 api-gtk
	✅ 🛠 tv-sim
	✅ 🛠 watch
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim

[webkit-commit-queue]

Committed 274102@main (c31a035): https://commits.webkit.org/274102@main

Reviewed commits have been landed. Closing PR #23854 and removing active labels.