better UIColor conversion

[tipa]

Description of Change

Better UIColor conversion uses rounding instead of cutting off decimals

Bugs Fixed

fixes #1572

API Changes

none

Behavioral Changes

none

PR Checklist

• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Updated documentation (see walkthrough)

[jamesmontemagno]

Anything for the other platforms at all?

[tipa]

@jamesmontemagno Windows & Android are using bytes for their "platform colors" so the bytes from the "system color" can be used 1:1

[jamesmontemagno]

Should also add some tests -> https://github.com/xamarin/Essentials/blob/main/Tests/Color_Tests.cs

[tipa]

Just spent an hour trying to add tests but the solution wouldn't build on my VS4Mac and on Windows, VS kept freezing when trying to start a remote session or the iOS simulator wouldn't launch.

This was the test I intended to try:

#if __IOS__
        [Fact]
        public void PlatformToColorDecimal()
        {
            var platform = UIKit.UIColor.FromDisplayP3(101.999986320734f, 50.9999969601631f, 153.000021278858f, a);
            var hex_platform = platform.ToString();
            var system = platform.ToSystemColor();
            var hex_system = system.ToString();
            Assert.Equal(hex_platform, hex_system);
        }
#endif

[jamesmontemagno]

@mattleibow good to go?