Simplify crating IconValues for UnifiedIcon from XAML

[Al12rs]

Simplified the various existing Setters on IconValue to be easier to use from XAML.

They now take the original types of string, IImage, Geometry instead of the custom types used internally by IconValue.
This allows them to be set them inline instead of having to wrap them in the custom types.

This maintains the single UnifiedIcon.Value Api, but reduces the number of lines needed to define the contents of an icon from XAML.

Before:

                <unifiedIcon:IconValue x:Key="ProjektankerIconValue">
                    <unifiedIcon:IconValue.ProjektankerIconValueSetter>
                        <unifiedIcon:ProjektankerIcon Value="mdi-cog" />
                    </unifiedIcon:IconValue.ProjektankerIconValueSetter>
                </unifiedIcon:IconValue>

After:

<unifiedIcon:IconValue x:Key="ProjektankerIconValue" MdiValueSetter="mdi-cog"/>

[erri120]

The types of the union should be changed back to init-only records. I converted them to have a getter and setter because XAML can't work with constructors.

// before
public class ProjektankerIcon
{
    public string? Value { get; set; }

    public ProjektankerIcon() { }

    public ProjektankerIcon(string? value)
    {
        Value = value;
    }
}

// after
public record ProjektankerIcon(string? Value);

[codecov-commenter]

Codecov Report

Attention: 9 lines in your changes are missing coverage. Please review.

Comparison is base (903e6fb) 58.67% compared to head (16d7e94) 58.74%.
Report is 2 commits behind head on main.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #953      +/-   ##
==========================================
+ Coverage   58.67%   58.74%   +0.06%     
==========================================
  Files         630      630              
  Lines       20253    20236      -17     
  Branches     1555     1555              
==========================================
+ Hits        11884    11888       +4     
+ Misses       8006     7987      -19     
+ Partials      363      361       -2     

Flag	Coverage Δ
Linux	58.05% <0.00%> (+0.01%)	⬆️
Windows	58.01% <0.00%> (+0.04%)	⬆️
clean_environment_tests	58.73% <0.00%> (+0.06%)	⬆️
network_tests	?

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Files	Coverage Δ
...xusMods.App.UI/Controls/UnifiedIcon/UnifiedIcon.cs	42.64% <0.00%> (ø)
...NexusMods.App.UI/Controls/UnifiedIcon/IconValue.cs	0.00% <0.00%> (ø)

... and 5 files with indirect coverage changes