[release/2.x] Add some new overloads for better compat

[mattleibow]

Description of Change

In SkiaSharp 3.x, the overloads no longer take the SKImageFilter.CropRect and instead use a plain SKRect.

This PR adds a bunch of overloads into the 2.x series that are present in 3.x - notably the SKImageFilter.CropRect to SKRect as well as some others. CreateShader is also new and really CreatePaint is a CreateShader under the hood in C++.

For the variations of CreateMatrix with the different in overloads, I will add this back into 3.x using the mechanism in #2789

Instead of a single overload with all the default parameters, the new overloads avoid defaults so we can not require nullable structs as well as not use the CropRect class if the crop rect is not in use.

After this PR lands, libraries that want to be compatible with 3.x will need to:

• Switch to the SKRect overloads
• Switch to CreateShader
• Switch to ReadOnlySpan overloads
• Recompile to get C# to pick the correct overloads if default parameters are used

Bugs Fixed

• Related to [release/2.x] Backport some new APIs from 3.0 to 2.x allowing smoother migration. #2756
• Related to Improve 3.x compatibility with 2.x (or vice versa) #2790

API Changes

None.

Behavioral Changes

None.

Required skia PR

None.

PR Checklist

• Has tests (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Merged related skia PRs
• Changes adhere to coding standard
• Updated documentation