Update includes to to be relative to src directory

Don't use relative imports like `../foo.h` as those depend on the
relative position of both files. Rather than that use imports relative
to the `src` directory, which explicitly is part of the include
directories.

src/components/heartrate/Biquad.cpp

@@ -4,7 +4,7 @@
   C++ port Copyright (C) 2021 Jean-François Milants
 */
 
-#include "Biquad.h"
+#include "components/heartrate/Biquad.h"
 
 using namespace Pinetime::Controllers;
 

src/components/heartrate/HeartRateController.cpp

@@ -1,4 +1,4 @@
-#include "HeartRateController.h"
+#include "components/heartrate/HeartRateController.h"
 #include <heartratetask/HeartRateTask.h>
 #include <systemtask/SystemTask.h>
 

src/components/heartrate/Ppg.cpp

@@ -6,7 +6,7 @@
 
 #include <vector>
 #include <nrf_log.h>
-#include "Ppg.h"
+#include "components/heartrate/Ppg.h"
 using namespace Pinetime::Controllers;
 
 /** Original implementation from wasp-os : https://github.com/daniel-thompson/wasp-os/blob/master/wasp/ppg.py */

src/components/heartrate/Ppg.h

@@ -1,8 +1,8 @@
 #pragma once
 
 #include <array>
-#include "Biquad.h"
-#include "Ptagc.h"
+#include "components/heartrate/Biquad.h"
+#include "components/heartrate/Ptagc.h"
 
 namespace Pinetime {
   namespace Controllers {

src/components/heartrate/Ptagc.cpp

@@ -5,7 +5,7 @@
 */
 
 #include <cmath>
-#include "Ptagc.h"
+#include "components/heartrate/Ptagc.h"
 
 using namespace Pinetime::Controllers;