Filesystem: Fixes for posix_rename and write (#3099)

* Fix rename

We shouldn't be leaving a copy of the original filename laying around.
This fixes one of a few broken savedata checks in DRAGON BALL XENOVERSE (CUSA01341)

* sceKernelWrite hack

Seems like std::fwrite has some weird edge cases we aren't handling properly.
Until we get to the bottom of this issue, here's a hack that bypasses it.
This fixes saves in DRAGON BALL XENOVERSE (CUSA01341)

* hack fix

* Improved "hack"

* Fix rename for Windows users

Turns out, we're using copy instead of rename for a reason, and that same reason came up when adding the remove call.
Also adds a log for the sceKernelWrite issue, since that's definitely a hack that needs to be debugged.

* A real fix for the sceKernelWrite issue

Turns out, some data was just buffered.
Running Flush fixes that problem.

* Move fflush call to WriteRaw

To prevent future cases of this issue.

src/common/io_file.h

@@ -186,7 +186,9 @@ public:
 
     template <typename T>
     size_t WriteRaw(const void* data, size_t size) const {
-        return std::fwrite(data, sizeof(T), size, file);
+        auto bytes = std::fwrite(data, sizeof(T), size, file);
+        std::fflush(file);
+        return bytes;
     }
 
     template <typename T>