Unify source of camera geometry data

Due to parallel development, camera pose information ended up being
populated in two constants files. This makes //y2019/vision:constants
the source for all of the constants.

Also, because the camera 19 calibration was done as if it was a front
camera, I had to negate its x/y position and offset the angle by 180
degrees.

This commit also adds validation for //y2019/vision:constants.cc to
ensure that it is not accidentally changed in a way that the codegen
cannot account for.

Change-Id: I85654d973e15ae7bf76589be63c3d0eaf72c3a45
diff --git a/y2019/vision/constants_formatting.cc b/y2019/vision/constants_formatting.cc
index 272246e..a2922a0 100644
--- a/y2019/vision/constants_formatting.cc
+++ b/y2019/vision/constants_formatting.cc
@@ -51,8 +51,9 @@
      << "\"" << filename_prefix << "\",\n        " << num_images << ",\n    }";
 }
 
-void DumpCameraConstants(int camera_id, const CameraCalibration &value) {
-  std::ofstream o("y2019/vision/constants.cc");
+void DumpCameraConstants(const char *fname, int camera_id,
+                         const CameraCalibration &value) {
+  std::ofstream o(fname);
   o << R"(#include "y2019/vision/constants.h"
 
 namespace y2019 {