Improve DirectoryInfo.GetDirectories exception details (dotnet#8725)

* Improve DirectoryInfo.GetDirectories exception details, fixes dotnet#8544

* Apply suggestions from code review

Author: adamsitnik

xml/System.IO/Directory.xml

@@ -2405,7 +2405,11 @@ An I/O error occurred.</exception>
           <paramref name="path" /> is <see langword="null" />.</exception>
         <exception cref="T:System.IO.PathTooLongException">The specified path, file name, or both exceed the system-defined maximum length.</exception>
         <exception cref="T:System.IO.IOException">
-          <paramref name="path" /> is a file name.</exception>
+          <paramref name="path" /> is a file name.
+
+ -or- 
+ 
+ File or directory is corrupted and unreadable (example: invalid first allocation unit of a FAT32 partition).</exception>    
         <exception cref="T:System.IO.DirectoryNotFoundException">The specified path is invalid (for example, it is on an unmapped drive).</exception>
         <altmember cref="M:System.IO.Directory.GetCurrentDirectory" />
         <related type="Article" href="/dotnet/standard/io/">File and Stream I/O</related>
@@ -2505,7 +2509,11 @@ An I/O error occurred.</exception>
           <paramref name="path" /> or <paramref name="searchPattern" /> is <see langword="null" />.</exception>
         <exception cref="T:System.IO.PathTooLongException">The specified path, file name, or both exceed the system-defined maximum length.</exception>
         <exception cref="T:System.IO.IOException">
-          <paramref name="path" /> is a file name.</exception>
+          <paramref name="path" /> is a file name.
+
+ -or- 
+ 
+ File or directory is corrupted and unreadable (example: invalid first allocation unit of a FAT32 partition).</exception>   
         <exception cref="T:System.IO.DirectoryNotFoundException">The specified path is invalid (for example, it is on an unmapped drive).</exception>
         <altmember cref="M:System.IO.Directory.GetCurrentDirectory" />
         <related type="Article" href="/dotnet/standard/io/">File and Stream I/O</related>
@@ -2589,7 +2597,11 @@ An I/O error occurred.</exception>
           <paramref name="path" /> or <paramref name="searchPattern" /> is <see langword="null" />.</exception>
         <exception cref="T:System.IO.PathTooLongException">The specified path, file name, or both exceed the system-defined maximum length.</exception>
         <exception cref="T:System.IO.IOException">
-          <paramref name="path" /> is a file name.</exception>
+          <paramref name="path" /> is a file name.
+
+ -or- 
+ 
+ File or directory is corrupted and unreadable (example: invalid first allocation unit of a FAT32 partition).</exception>   
         <exception cref="T:System.IO.DirectoryNotFoundException">The specified path is invalid (for example, it is on an unmapped drive).</exception>
       </Docs>
     </Member>
@@ -2685,7 +2697,11 @@ An I/O error occurred.</exception>
         <exception cref="T:System.UnauthorizedAccessException">The caller does not have the required permission.</exception>
         <exception cref="T:System.IO.PathTooLongException">The specified path, file name, or both exceed the system-defined maximum length.</exception>
         <exception cref="T:System.IO.IOException">
-          <paramref name="path" /> is a file name.</exception>
+          <paramref name="path" /> is a file name.
+
+ -or- 
+ 
+ File or directory is corrupted and unreadable (example: invalid first allocation unit of a FAT32 partition).</exception>   
         <exception cref="T:System.IO.DirectoryNotFoundException">The specified path is invalid (for example, it is on an unmapped drive).</exception>
         <altmember cref="M:System.IO.Directory.GetCurrentDirectory" />
         <related type="Article" href="/dotnet/standard/io/">File and Stream I/O</related>