Re-organize dvr_tracking headers

1/ dvr_tracking_types.h is public header, include it in dvr_api.h
2/ dvr_tracking.h is private header, only include it in dvr_api.cpp
3/ Forward declare DvrTrackingXXX opaque handles and callback
   signatures in dvr_api.h

Bug: 78169521
Test: Build system
Change-Id: I5583dd7ad6a403fd4f2429770f30c1ba696e8430
diff --git a/libs/vr/libdvr/dvr_api.cpp b/libs/vr/libdvr/dvr_api.cpp
index d14f040..e099f6a 100644
--- a/libs/vr/libdvr/dvr_api.cpp
+++ b/libs/vr/libdvr/dvr_api.cpp
@@ -12,6 +12,7 @@
 #include <dvr/dvr_display_manager.h>
 #include <dvr/dvr_performance.h>
 #include <dvr/dvr_surface.h>
+#include <dvr/dvr_tracking.h>
 #include <dvr/dvr_vsync.h>
 
 // Headers not yet moved into libdvr.