Improve shadow rendering on Android, fix shadow clipping on iOS

[albyrock87]

Android Shadow Rendering

Description of Change

• move the shadow computation to android level with an improved algorithm
  • use Glide's LruBitmapPool to reduce the memory pressure on Java
  • prepare Paint only when shadow changes
• when we know we're going to render a solid shape we can use Canvas API to speedup the shadow rendering performance by a lot
• remove unneeded saveLayer call from platform interop: it's a very expensive operation done for no reasons here
• fix shadow rendering on Android which was still broken (despite Shadows not rendering as expected on Android and iOS #24414) under some conditions (like negative offsets)

Benchmark

Here I've executed the testing host app with return new ShadowBenchmark(); as main page and scrolling the CV once.

Before

After (with transparency)

You can see this is a bit faster, and for sure it is creating less GC/allocation work due to the bitmap pool.
Still timings are not good enough.

After (with solid background)

This time no need to create bitmaps and render descendants, we can simply draw the shadow.
And this is exactly the speed we want.

Notes

To collect those speedscopes I've temporary re-added:

protected override void DrawShadow(Canvas canvas, int viewWidth, int viewHeight)
{
	base.DrawShadow(canvas, viewWidth, viewHeight);
}

iOS Shadow Rendering

• Removes unneeded shadow sublayer from wrapper view => we can simply apply the shadow to the WrapperView's main Layer considering it's the parent of the clipped content.
• Make clear that the layer where we apply clipping is the content's main Layer
• Ensure that when the clip is removed, we also clear the content's Layer's mask

Issues Fixed

Fixes #27156
Fixes #23630
Fixes #20518
Fixes #18202
Fixes #17886
Fixes #13981
Fixes #9539
Fixes #4106

Relates to #17881
Relates to #17257
Relates to #10401

[PureWeen]

/azp run

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[PureWeen]

/rebase

[PureWeen]

/azp run

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[AmrAlSayed0]

I'm late to the party but an attempt to improve shadow's performance was made before here #10523. Moving the code to the Java side might help but I think what would benefit the most is a shadow cache. All views that have the same size and the same shadow properties (very common scenario in CollectionView items for example) should use the same bitmap. This will eliminate a huge number of calls including C# to Java ones. There is an implementation of the shadow cache in the PR.

[albyrock87]

@AmrAlSayed0 thanks for sharing, I'll check it out.
This is still a very early WIP.
I also intend using Glide's bitmap pool for this, which should improve the performance by avoiding continuous allocations of the bitmaps.

[albyrock87]

This PR depends on #27531 to fix MacCatalyst screenshot taking.

[PureWeen]

/rebase

[PureWeen]

/azp run

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[albyrock87]

Failing tests look unrelated.

[jsuarezruiz]

Added some Device Tests to validate the IsSolid extension method.

[jsuarezruiz]

/azp run

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[jsuarezruiz]

Rebased and updated macOS snapshots after merge #27531

[jsuarezruiz]

/azp run

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