tag/Id3Load, ...: use std::make_unique_for_overwrite()

Don't zero-initialize the buffers.  This removes some useless
overhead.

src/io/uring/ReadOperation.cxx

@@ -17,7 +17,7 @@ ReadOperation::Start(Queue &queue, FileDescriptor fd, off_t offset,
 
 	handler = &_handler;
 
-	buffer = std::make_unique<std::byte[]>(size);
+	buffer = std::make_unique_for_overwrite<std::byte[]>(size);
 
 	auto &s = queue.RequireSubmitEntry();