Fixed ExpressionNode.EnsureReferenceInfo() crash with .NET Native (#4014)

## Closes #4011
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<!-- Add a brief overview here of the feature/bug & fix. -->

## PR Type
What kind of change does this PR introduce?
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- Bugfix
<!-- - Feature -->
<!-- - Code style update (formatting) -->
<!-- - Refactoring (no functional changes, no api changes) -->
<!-- - Build or CI related changes -->
<!-- - Documentation content changes -->
<!-- - Sample app changes -->
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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying, or link to a relevant issue. -->
Crash with .NET Native, documented in the related issue.

## What is the new behavior?
<!-- Describe how was this issue resolved or changed? -->
The logic has been changed to not rely on APIs that might have a behavioral change under .NET Native.

## PR Checklist

Please check if your PR fulfills the following requirements:

- [X] Tested code with current [supported SDKs](../readme.md#supported)
- [ ] ~~Pull Request has been submitted to the documentation repository [instructions](..\contributing.md#docs). Link: <!-- docs PR link -->~~
- [ ] ~~Sample in sample app has been added / updated (for bug fixes / features)~~
    - [ ] ~~Icon has been created (if new sample) following the [Thumbnail Style Guide and templates](https://github.com/windows-toolkit/WindowsCommunityToolkit-design-assets)~~
- [X] New major technical changes in the toolkit have or will be added to the [Wiki](https://github.com/windows-toolkit/WindowsCommunityToolkit/wiki) e.g. build changes, source generators, testing infrastructure, sample creation changes, etc...
- [X] Tests for the changes have been added (for bug fixes / features) (if applicable)
- [X] Header has been added to all new source files (run *build/UpdateHeaders.bat*)
- [X] Contains **NO** breaking changes

Author: msftbot[bot]

Microsoft.Toolkit.Uwp.UI.Animations/Expressions/ExpressionNodes/ExpressionNode.cs

@@ -282,14 +282,10 @@ internal void EnsureReferenceInfo()
                 }
 
                 // Create a map to store the generated paramNames for each CompObj
-                uint id = 0;
                 _compObjToParamNameMap = new Dictionary<CompositionObject, string>();
                 foreach (var compObj in compObjects)
                 {
-                    // compObj.ToString() will return something like "Windows.UI.Composition.SpriteVisual"
-                    // Make it look like "SpriteVisual_1"
-                    string paramName = compObj.ToString();
-                    paramName = $"{paramName.Substring(paramName.LastIndexOf('.') + 1)}_{++id}";       // make sure the created param name doesn't overwrite a custom name
+                    string paramName = Guid.NewGuid().ToUppercaseAsciiLetters();
 
                     _compObjToParamNameMap.Add(compObj, paramName);
                 }

Microsoft.Toolkit.Uwp.UI.Animations/Extensions/System/GuidExtensions.cs

@@ -0,0 +1,36 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Diagnostics.Contracts;
+
+namespace Microsoft.Toolkit.Uwp.UI.Animations
+{
+    /// <summary>
+    /// An extension <see langword="class"/> for the <see cref="Guid"/> type
+    /// </summary>
+    internal static class GuidExtensions
+    {
+        /// <summary>
+        /// Returns a <see cref="string"/> representation of a <see cref="Guid"/> only made of uppercase letters
+        /// </summary>
+        /// <param name="guid">The input <see cref="Guid"/> to process</param>
+        /// <returns>A <see cref="string"/> representation of <paramref name="guid"/> only made up of letters in the [A-Z] range</returns>
+        [Pure]
+        public static string ToUppercaseAsciiLetters(in this Guid guid)
+        {
+            // Composition IDs must only be composed of characters in the [A-Z0-9_] set,
+            // and also have the restriction that the initial character cannot be a digit.
+            // Because of this, we need to prepend an underscore to a serialized guid to
+            // avoid cases where the first character is a digit. Additionally, we're forced
+            // to use ToUpper() here because ToString("N") currently returns a lowercase
+            // hexadecimal string. Note: this extension might be improved once we move to
+            // .NET 5 in the WinUI 3 release, by using string.Create<TState>(...) to only
+            // have a single string allocation, and then using Guid.TryFormat(...) to
+            // serialize the guid in place over the Span<char> starting from the second
+            // character. For now, this implementation is fine on UWP and still fast enough.
+            return $"_{guid.ToString("N").ToUpper()}";
+        }
+    }
+}

Microsoft.Toolkit.Uwp.UI.Media/Extensions/System/GuidExtensions.cs

@@ -6,6 +6,7 @@
 using System.Diagnostics.Contracts;
 using System.Threading.Tasks;
 using Microsoft.Graphics.Canvas.Effects;
+using Microsoft.Toolkit.Uwp.UI.Animations;
 using Windows.Graphics.Effects;
 using Windows.UI;
 using Windows.UI.Composition;

Microsoft.Toolkit.Uwp.UI.Media/Pipelines/PipelineBuilder.Effects.Internals.cs

@@ -8,6 +8,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Graphics.Canvas.Effects;
+using Microsoft.Toolkit.Uwp.UI.Animations;
 using Windows.Graphics.Effects;
 using Windows.UI;
 using Windows.UI.Composition;

Microsoft.Toolkit.Uwp.UI.Media/Pipelines/PipelineBuilder.Effects.cs

@@ -8,6 +8,7 @@
 using System.Threading.Tasks;
 using Microsoft.Graphics.Canvas;
 using Microsoft.Graphics.Canvas.Effects;
+using Microsoft.Toolkit.Uwp.UI.Animations;
 using Microsoft.Toolkit.Uwp.UI.Media.Helpers;
 using Microsoft.Toolkit.Uwp.UI.Media.Helpers.Cache;
 using Windows.Graphics.Effects;

Microsoft.Toolkit.Uwp.UI.Media/Pipelines/PipelineBuilder.Initialization.cs

@@ -8,6 +8,7 @@
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.Graphics.Canvas.Effects;
+using Microsoft.Toolkit.Uwp.UI.Animations;
 using Windows.Graphics.Effects;
 using Windows.UI.Composition;
 using CanvasBlendEffect = Microsoft.Graphics.Canvas.Effects.BlendEffect;

Microsoft.Toolkit.Uwp.UI.Media/Pipelines/PipelineBuilder.Merge.cs

@@ -6,6 +6,7 @@
 using System.Collections.Generic;
 using System.Diagnostics.Contracts;
 using System.Threading.Tasks;
+using Microsoft.Toolkit.Uwp.UI.Animations;
 using Windows.Graphics.Effects;
 using Windows.UI.Composition;
 using Windows.UI.Xaml;