update the docs for System.Runtime.CompilerServices.Unsafe (dotnet#4081)

* update the docs for SRCS

* Update AsyncValueTaskMethodBuilder`1.xml

* Update ValueTaskAwaiter`1.xml

Author: Anipik

xml/System.Runtime.CompilerServices/AsyncValueTaskMethodBuilder`1.xml

@@ -34,7 +34,7 @@
   </Base>
   <Interfaces />
   <Docs>
-    <typeparam name="TResult">To be added.</typeparam>
+    <typeparam name="TResult">The type of the result produced by the task.</typeparam>
     <summary>Represents a builder for asynchronous methods that returns a <see cref="T:System.Threading.Tasks.ValueTask`1" />.</summary>
     <remarks>To be added.</remarks>
   </Docs>

xml/System.Runtime.CompilerServices/ConfiguredValueTaskAwaitable`1+ConfiguredValueTaskAwaiter.xml

@@ -48,6 +48,7 @@
   </Attributes>
   <Docs>
     <summary>Provides an awaiter for a <see cref="T:System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable`1" />.</summary>
+    <typeparam name="TResult">The type of the result produced by the task.</typeparam>
     <remarks>To be added.</remarks>
   </Docs>
   <Members>

xml/System.Runtime.CompilerServices/TupleElementNamesAttribute.xml

@@ -74,7 +74,7 @@
       </AssemblyInfo>
       <Parameters />
       <Docs>
-        <summary>To be added.</summary>
+        <summary>>Initializes a new instance of the <see cref="T:System.Runtime.CompilerServices.TupleElementNamesAttribute" /> class.</summary>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>

xml/System.Runtime.CompilerServices/ValueTaskAwaiter`1.xml

@@ -46,7 +46,7 @@
     </Attribute>
   </Attributes>
   <Docs>
-    <typeparam name="TResult">To be added.</typeparam>
+    <typeparam name="TResult">The type of the result produced by the task.</typeparam>
     <summary>Provides an awaiter for a <see cref="T:System.Threading.Tasks.ValueTask`1" />.</summary>
     <remarks>To be added.</remarks>
   </Docs>
@@ -81,7 +81,7 @@
       <Parameters />
       <Docs>
         <summary>Gets the result of the ValueTask.</summary>
-        <returns>To be added.</returns>
+        <returns>The result of the completed task.</returns>
         <remarks>To be added.</remarks>
       </Docs>
     </Member>
@@ -153,7 +153,7 @@
         <Parameter Name="continuation" Type="System.Action" />
       </Parameters>
       <Docs>
-        <param name="continuation">To be added.</param>
+        <param name="continuation">The action to perform when the wait operation completes.</param>
         <summary>Schedules the continuation action for this <see cref="T:System.Threading.Tasks.ValueTask`1" />.</summary>
         <remarks>To be added.</remarks>
       </Docs>