Add information about when the target is considered not initialized when using an overload that doesn't provide the initialized flag (#3446)

* Add information about when the target is considered not initialized when using an overload that doesn't provide the initialized flag.

* Added clarification for when it's considered initialized or not.

* Update xml/System.Threading/LazyInitializer.xml

Co-Authored-By: Maira Wenzel <[email protected]>

* Update xml/System.Threading/LazyInitializer.xml

Co-Authored-By: Maira Wenzel <[email protected]>

Co-authored-by: Maira Wenzel <[email protected]>

Author: paulomorgado

xml/System.Threading/LazyInitializer.xml

@@ -116,7 +116,7 @@ ExpensiveData dataToUse = LazyInitializer.EnsureInitialized(ref _data, ref _data
       </Parameters>
       <Docs>
         <typeparam name="T">The type of the reference to be initialized.</typeparam>
-        <param name="target">A reference to initialize if it has not already been initialized.</param>
+        <param name="target">A reference to initialize if it has not already been initialized. If it is <see langword="null" />, it is considered not initialized; otherwise, it's considered initialized.</param>
         <summary>Initializes a target reference type with the type's parameterless constructor if it hasn't already been initialized.</summary>
         <returns>The initialized object.</returns>
         <remarks>
@@ -295,7 +295,7 @@ ExpensiveData dataToUse = LazyInitializer.EnsureInitialized(ref _data, ref _data
       </Parameters>
       <Docs>
         <typeparam name="T">The type of the reference to be initialized.</typeparam>
-        <param name="target">A reference to initialize if it has not already been initialized.</param>
+        <param name="target">A reference to initialize if it has not already been initialized. If it is <see langword="null" />, it is considered not initialized; otherwise, it's considered initialized.</param>
         <param name="syncLock">A reference to an object used as the mutually exclusive lock for initializing
             <paramref name="target" />. If <paramref name="syncLock" /> is <see langword="null" />, a new object will be instantiated.</param>
         <param name="valueFactory">The method to invoke to initialize <paramref name="target" />.</param>