disk_archive: Remove unused total_entries_in_directory member from DiskDirectory

Also converts initializer list assignments to in-class initializers
where relevant.

src/core/file_sys/disk_archive.cpp

@@ -52,7 +52,7 @@ bool DiskFile::Close() const {
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
-DiskDirectory::DiskDirectory(const std::string& path) : directory() {
+DiskDirectory::DiskDirectory(const std::string& path) {
     unsigned size = FileUtil::ScanDirectoryTree(path, directory);
     directory.size = size;
     directory.isDirectory = true;

src/core/file_sys/disk_archive.h

@@ -59,8 +59,7 @@ public:
     }
 
 protected:
-    u32 total_entries_in_directory;
-    FileUtil::FSTEntry directory;
+    FileUtil::FSTEntry directory{};
 
     // We need to remember the last entry we returned, so a subsequent call to Read will continue
     // from the next one.  This iterator will always point to the next unread entry.