fix(cppclient): Remove extension from dhclient and dhcore for cross-p…

…latform compatibility (deephaven#5706)

Windows expects .dll and Linux expects .so, but the machinery behind
LibraryImport seems to know to do the right thing.

csharp/client/DeephavenClient/Interop/InteropSupport.cs

@@ -6,8 +6,8 @@
 namespace Deephaven.DeephavenClient.Interop;
 
 internal class LibraryPaths {
-  internal const string Dhcore = "dhcore.dll";
-  internal const string Dhclient = "dhclient.dll";
+  internal const string Dhcore = "dhcore";
+  internal const string Dhclient = "dhclient";
 }
 
 /// <summary>