LibAudio: Add a sample count hinting mechanism to audio encoding

Author: https://github.com/kleinesfilmroellchen
Commit: b4b411b8a3
Pull-request: https://github.com/SerenityOS/serenity/pull/20650

Userland/Utilities/aconv.cpp

@@ -141,6 +141,9 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
             return 1;
         }
 
+        if (writer.has_value())
+            (*writer)->sample_count_hint(input_loader->total_samples());
+
         if (output != "-"sv)
             out("Writing: \033[s");