Move xfa/include/fxjse/fxjse.h into xfa/fxjse/include.

This CL moves the fxjse.h header and splits the cfxjse_arguments.h into its
own file.

R=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1807623002 .
diff --git a/fpdfsdk/include/javascript/IJavaScript.h b/fpdfsdk/include/javascript/IJavaScript.h
index 6b15467..3196348 100644
--- a/fpdfsdk/include/javascript/IJavaScript.h
+++ b/fpdfsdk/include/javascript/IJavaScript.h
@@ -11,7 +11,7 @@
 #include "core/include/fxcrt/fx_system.h"
 
 #ifdef PDF_ENABLE_XFA
-#include "xfa/include/fxjse/fxjse.h"
+#include "xfa/fxjse/include/fxjse.h"
 #endif  // PDF_ENABLE_XFA
 
 class CPDFDoc_Environment;