faces/pulsometer: move structure definition

Instances of the pulsometer state structure are only passed
to the pulsometer itself and only via the opaque context pointer.
No other code uses it. There is no need to expose it in a header file
so make it an implementation detail of the watch face.

movement/watch_faces/complication/pulsometer_face.c

@@ -51,6 +51,13 @@
 
 #define PULSOMETER_FACE_FREQUENCY (1 << PULSOMETER_FACE_FREQUENCY_FACTOR)
 
+typedef struct {
+    bool measuring;
+    int16_t pulses;
+    int16_t ticks;
+    int8_t calibration;
+} pulsometer_state_t;
+
 static void pulsometer_display_title(pulsometer_state_t *pulsometer) {
     watch_display_string(PULSOMETER_FACE_TITLE, 0);
 }