Outset box shadow impl

[joevilches]

Summary: tisa. Algo is

• Draw offscreen rect the size of the outset shadow (so accounting for spread)
• Set g state to cast shadow in proper place ON screen
• Clear out region in view

The rects need to be offscreen for the following reasons

• We need to account for spread radius, and CGContext shadows do not have support for this. So the only way to create a bigger shadow is the create a path that is the same size as the shadow we want
• We cannot just position this rect onscreen with no offset (so the shadow is casting directly under it) since the blur will look unnatural
• Offscreen means we do not see filled shadow rect but we do see the shadow it casts by offsetting it in the proper location

Reviewed By: lenaic

Differential Revision: D58881588

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D58881588

[analysis-bot]

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	20,300,550	+98,475
android	hermes	armeabi-v7a	n/a	--
android	hermes	x86	n/a	--
android	hermes	x86_64	n/a	--
android	jsc	arm64-v8a	23,497,363	+98,482
android	jsc	armeabi-v7a	n/a	--
android	jsc	x86	n/a	--
android	jsc	x86_64	n/a	--

Base commit: f473a2f8f48ed8ce94a1f8a3181a5dabb4c6ad8d Branch: main