Clarify Type.FullName and Type.AssemblyQualifiedName null return conditions (#12106)

Fixes #12104

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jkotas <6668460+jkotas@users.noreply.github.com>

Author: Copilot

xml/System/Type.xml

@@ -311,7 +311,7 @@ The code example uses the <xref:System.Reflection.MethodInfo> to invoke the <xre
       </ReturnValue>
       <Docs>
         <summary>Gets the assembly-qualified name of the type, which includes the name of the assembly from which this <see cref="T:System.Type" /> object was loaded.</summary>
-        <value>The assembly-qualified name of the <see cref="T:System.Type" />, which includes the name of the assembly from which the <see cref="T:System.Type" /> was loaded, or <see langword="null" /> if the current instance represents a generic type parameter.</value>
+        <value>The assembly-qualified name of the <see cref="T:System.Type" />, which includes the name of the assembly from which the <see cref="T:System.Type" /> was loaded, or <see langword="null" /> if the type can't be represented by an assembly-qualified name. Types that can't be represented by an assembly-qualified name include types that contain unresolved generic parameters (<see cref="P:System.Type.ContainsGenericParameters" /> is <see langword="true" />) and types that contain function pointers.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[
 
@@ -1593,7 +1593,7 @@ The `filter` argument can be a custom delegate of type <xref:System.Reflection.M
       </ReturnValue>
       <Docs>
         <summary>Gets the fully qualified name of the type, including its namespace but not its assembly.</summary>
-        <value>The fully qualified name of the type, including its namespace but not its assembly; or <see langword="null" /> if the current instance represents a generic type parameter, an array type, pointer type, or <see langword="byref" /> type based on a type parameter, or a generic type that is not a generic type definition but contains unresolved type parameters.</value>
+        <value>The fully qualified name of the type, including its namespace but not its assembly; or <see langword="null" /> if the type can't be represented by a fully qualified name. Types that can't be represented by a fully qualified name include types that contain unresolved generic parameters (<see cref="P:System.Type.ContainsGenericParameters" /> is <see langword="true" />) and types that contain function pointers.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[