Port System.Xml new docs (#10161)

* System.Xml

* System.Xml.Linq

* Apply suggestions from code review

Co-authored-by: Genevieve Warren <[email protected]>

---------

Co-authored-by: Genevieve Warren <[email protected]>

Author: carlossanlop

xml/System.Xml.Linq/XName.xml

@@ -508,6 +508,7 @@ http://www.adventure-works.com
         </remarks>
         <altmember cref="P:System.Xml.Linq.XName.Namespace" />
         <related type="Article" href="/dotnet/standard/linq/linq-xml-overview">LINQ to XML overview</related>
+        <seealso cref="P:System.Xml.Linq.XName.Namespace" />
       </Docs>
     </Member>
     <Member MemberName="Namespace">

xml/System.Xml/XmlResolver.xml

@@ -208,9 +208,9 @@ resolver.Credentials = myCache;
         <ReturnType>System.Xml.XmlResolver</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>To be added.</summary>
-        <value>To be added.</value>
-        <remarks>To be added.</remarks>
+        <summary>Gets an XML resolver that resolves only file system URIs.</summary>
+        <value>An XML resolver that resolves only file system URIs.</value>
+        <remarks>Calling <see cref="M:System.Xml.XmlResolver.GetEntity(System.Uri,System.String,System.Type)" /> or <see cref="M:System.Xml.XmlResolver.GetEntityAsync(System.Uri,System.String,System.Type)" /> on the <see cref="T:System.Xml.XmlResolver" /> instance returned by this property resolves only URIs whose scheme is file.</remarks>
       </Docs>
     </Member>
     <Member MemberName="GetEntity">