Fixed some nullability warnings

Author: Sergio0694

Microsoft.Toolkit.HighPerformance/Extensions/ArrayExtensions.2D.cs

@@ -63,7 +63,7 @@ public static ref T DangerousGetReference<T>(this T[,] array)
         public static ref T DangerousGetReferenceAt<T>(this T[,] array, int i, int j)
         {
 #if NETCORE_RUNTIME
-            var arrayData = Unsafe.As<RawArray2DData>(array);
+            var arrayData = Unsafe.As<RawArray2DData>(array)!;
             nint offset = ((nint)(uint)i * (nint)(uint)arrayData.Width) + (nint)(uint)j;
             ref T r0 = ref Unsafe.As<byte, T>(ref arrayData.Data);
             ref T ri = ref Unsafe.Add(ref r0, offset);

Microsoft.Toolkit.HighPerformance/Extensions/ArrayExtensions.3D.cs

@@ -32,7 +32,7 @@ public static partial class ArrayExtensions
         public static ref T DangerousGetReference<T>(this T[,,] array)
         {
 #if NETCORE_RUNTIME
-            var arrayData = Unsafe.As<RawArray3DData>(array);
+            var arrayData = Unsafe.As<RawArray3DData>(array)!;
             ref T r0 = ref Unsafe.As<byte, T>(ref arrayData.Data);
 
             return ref r0;
@@ -63,7 +63,7 @@ public static ref T DangerousGetReference<T>(this T[,,] array)
         public static ref T DangerousGetReferenceAt<T>(this T[,,] array, int i, int j, int k)
         {
 #if NETCORE_RUNTIME
-            var arrayData = Unsafe.As<RawArray3DData>(array);
+            var arrayData = Unsafe.As<RawArray3DData>(array)!;
             nint offset =
                 ((nint)(uint)i * (nint)(uint)arrayData.Height * (nint)(uint)arrayData.Width) +
                 ((nint)(uint)j * (nint)(uint)arrayData.Width) + (nint)(uint)k;

Microsoft.Toolkit.HighPerformance/Memory/Memory2D{T}.cs

@@ -772,7 +772,7 @@ public bool TryGetMemory(out Memory<T> memory)
                 }
                 else if (typeof(T) == typeof(char) && this.instance.GetType() == typeof(string))
                 {
-                    string text = Unsafe.As<string>(this.instance);
+                    string text = Unsafe.As<string>(this.instance)!;
                     int index = text.AsSpan().IndexOf(in text.DangerousGetObjectDataReferenceAt<char>(this.offset));
                     ReadOnlyMemory<char> temp = text.AsMemory(index, (int)Length);
 
@@ -795,7 +795,7 @@ public bool TryGetMemory(out Memory<T> memory)
                 else if (this.instance.GetType() == typeof(T[]))
                 {
                     // If it's a T[] array, also handle the initial offset
-                    T[] array = Unsafe.As<T[]>(this.instance);
+                    T[] array = Unsafe.As<T[]>(this.instance)!;
                     int index = array.AsSpan().IndexOf(ref array.DangerousGetObjectDataReferenceAt<T>(this.offset));
 
                     memory = array.AsMemory(index, this.height * this.width);

Microsoft.Toolkit.HighPerformance/Memory/ReadOnlyMemory2D{T}.cs

@@ -794,7 +794,7 @@ public bool TryGetMemory(out ReadOnlyMemory<T> memory)
                     // difference between the start of the Span<char> (which directly wraps just the actual character data
                     // within the string), and the input reference, which we can get from the byte offset in use. The result
                     // is the character index which we can use to create the final Memory<char> instance.
-                    string text = Unsafe.As<string>(this.instance);
+                    string text = Unsafe.As<string>(this.instance)!;
                     int index = text.AsSpan().IndexOf(in text.DangerousGetObjectDataReferenceAt<char>(this.offset));
                     ReadOnlyMemory<char> temp = text.AsMemory(index, (int)Length);
 
@@ -811,7 +811,7 @@ public bool TryGetMemory(out ReadOnlyMemory<T> memory)
                 else if (this.instance.GetType() == typeof(T[]))
                 {
                     // If it's a T[] array, also handle the initial offset
-                    T[] array = Unsafe.As<T[]>(this.instance);
+                    T[] array = Unsafe.As<T[]>(this.instance)!;
                     int index = array.AsSpan().IndexOf(ref array.DangerousGetObjectDataReferenceAt<T>(this.offset));
 
                     memory = array.AsMemory(index, this.height * this.width);