Add missing xml docs for System.Numerics (#106290)

* Add missing xml docs for System.Numerics

* Update src/libraries/System.Private.CoreLib/src/System/Numerics/TotalOrderIeee754Comparer.cs

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

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Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

src/libraries/System.Private.CoreLib/src/System/Numerics/TotalOrderIeee754Comparer.cs

@@ -226,8 +226,13 @@ public int GetHashCode([DisallowNull] T obj)
 
         public bool Equals(TotalOrderIeee754Comparer<T> other) => true;
 
+        /// <summary>Determines whether this instance and a specified object are equal.</summary>
+        /// <param name="obj">The object to compare with the current instance.</param>
+        /// <returns><c>true</c> if the current instance and <paramref name="obj" /> are equal; otherwise, <c>false</c>. If <paramref name="obj" /> is <c>null</c>, the method returns <c>false</c>.</returns>
         public override bool Equals([NotNullWhen(true)] object? obj) => obj is TotalOrderIeee754Comparer<T>;
 
+        /// <summary>Returns the hash code for this instance.</summary>
+        /// <returns>The hash code.</returns>
         public override int GetHashCode() => EqualityComparer<T>.Default.GetHashCode();
     }
 }

src/libraries/System.Runtime.Numerics/src/System/Numerics/Complex.cs

@@ -2200,6 +2200,7 @@ public static bool TryParse([NotNullWhen(true)] string? s, NumberStyles style, I
         public bool TryFormat(Span<char> destination, out int charsWritten, [StringSyntax(StringSyntaxAttribute.NumericFormat)] ReadOnlySpan<char> format = default, IFormatProvider? provider = null) =>
             TryFormatCore(destination, out charsWritten, format, provider);
 
+        /// <inheritdoc cref="IUtf8SpanFormattable.TryFormat(Span{byte}, out int, ReadOnlySpan{char}, IFormatProvider?)" />
         public bool TryFormat(Span<byte> utf8Destination, out int bytesWritten, [StringSyntax(StringSyntaxAttribute.NumericFormat)] ReadOnlySpan<char> format = default, IFormatProvider? provider = null) =>
             TryFormatCore(utf8Destination, out bytesWritten, format, provider);