[hal] Convert DutyCycle Raw output to be a high time measurement (#4466)

The existing raw time has an issue where it jumps around, as in the FPGA if the frequency is not a multiple or divisor of 25 Mhz it jumps around by 1 every second. While waiting on an FPGA change, update the API to make raw output give nanoseconds rather then a scaled value. This does a longer read cycle to get the correct value, but in the future if a fast FPGA function is added this can be easily changed.

wpilibc/src/main/native/include/frc/DutyCycle.h

@@ -7,6 +7,7 @@
 #include <memory>
 
 #include <hal/Types.h>
+#include <units/time.h>
 #include <wpi/sendable/Sendable.h>
 #include <wpi/sendable/SendableHelper.h>
 
@@ -83,21 +84,18 @@ class DutyCycle : public wpi::Sendable, public wpi::SendableHelper<DutyCycle> {
   double GetOutput() const;
 
   /**
-   * Get the raw output ratio of the duty cycle signal.
+   * Get the raw high time of the duty cycle signal.
    *
-   * <p> 0 means always low, an output equal to
-   * GetOutputScaleFactor() means always high.
-   *
-   * @return output ratio in raw units
+   * @return high time of last pulse
    */
-  unsigned int GetOutputRaw() const;
+  units::second_t GetHighTime() const;
 
   /**
    * Get the scale factor of the output.
    *
    * <p> An output equal to this value is always high, and then linearly scales
-   * down to 0. Divide the result of getOutputRaw by this in order to get the
-   * percentage between 0 and 1.
+   * down to 0. Divide a raw result by this in order to get the
+   * percentage between 0 and 1. Used by DMA.
    *
    * @return the output scale factor
    */