Port System & System.Numerics new docs (#10152)

* System.Numerics
* System
* System.Numerics.Tensors
---------
Co-authored-by: Genevieve Warren <[email protected]>

Author: carlossanlop

xml/System.Numerics.Tensors/ReadOnlyTensorSpan`1+Enumerator.xml

@@ -42,7 +42,7 @@
     </Attribute>
   </Attributes>
   <Docs>
-    <summary>To be added.</summary>
+    <summary>Enumerates the elements of a <see cref="T:System.Numerics.Tensors.ReadOnlyTensorSpan`1" />.</summary>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>
@@ -68,7 +68,7 @@
         <ReturnType>T</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
+        <summary>Gets the element at the current position of the enumerator.</summary>
         <value>To be added.</value>
         <remarks>To be added.</remarks>
       </Docs>
@@ -90,7 +90,7 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
+        <summary>Advances the enumerator to the next element of the span.</summary>
         <returns>To be added.</returns>
         <remarks>To be added.</remarks>
       </Docs>

xml/System.Numerics.Tensors/ReadOnlyTensorSpan`1.xml

@@ -42,7 +42,7 @@
     </Attribute>
   </Attributes>
   <Docs>
-    <summary>To be added.</summary>
+    <summary>Enumerates the elements of a <see cref="T:System.Numerics.Tensors.TensorSpan`1" />.</summary>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>
@@ -62,7 +62,7 @@
         <ReturnType>T</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
+        <summary>Gets the element at the current position of the enumerator.</summary>
         <value>To be added.</value>
         <remarks>To be added.</remarks>
       </Docs>
@@ -84,7 +84,7 @@
       </ReturnValue>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
+        <summary>Advances the enumerator to the next element of the span.</summary>
         <returns>To be added.</returns>
         <remarks>To be added.</remarks>
       </Docs>