rawinput: distinguish between circular and linear analog input (#665)

## Link to GitHub Issue or related Pull Request, if one exists
n/a

## Description of change
Currently, all analogs are treated as circular values that wrap around.
This works for knobs and turntables, but can get weird for linear values
(like tilt sensors and sliders) especially once analog options are
enabled, such as sensitivity.

This PR groups analogs into 3 buckets: circular, linear (centered), and
linear (positive). Linear types get different algorithms applied to it
when options are set (e.g., sensitivity caps out at 0, 1 instead of
wrapping around).

In linear mode:
* Sensitivity value applies an exponential response curve (power curve)
to the original value.
* Multiplier/divisor serves as a linear cut-off.
* Relative mode works as you expect, but of course, values don't wrap
around.
* Invert and deadzone work as you expect (since they applied to the
controller input anyway)
* Smoothing is removed from the UI and has no effect.
* Delay is unaffected.

Also, fix a small bug with -/+ button not working for analog `Delay`
option.

## Testing
WIP

src/spice2x/cfg/analog.h

@@ -13,6 +13,21 @@ namespace rawinput {
     class RawInputManager;
 }
 
+namespace GameAPI::Analogs {
+    enum class AnalogType {
+        // default; values wrap around (below 0 turns into 1, over 1 is 0)
+        // knobs, turntables
+        Circular = 0,
+
+        // typical joystick that rests at the center and caps at [0, 1]
+        LinearCentered = 1,
+
+        // one-directional value (sliders and instruments like piano/drum velocity)
+        // starts at 0 and goes up to 1
+        LinearPositive = 2,
+    };
+}
+
 struct AnalogMovingAverage {
     double time_in_ms;
     float sine;
@@ -31,10 +46,11 @@ private:
     float last_state = 0.5f;
     bool sensitivity_set = false;
     bool deadzone_set = false;
+    GameAPI::Analogs::AnalogType type = GameAPI::Analogs::AnalogType::Circular;
     
     // smoothing function
     bool smoothing = false;
-    std::array<AnalogMovingAverage, ANALOG_HISTORY_CNT> vector_history;
+    std::array<AnalogMovingAverage, ANALOG_HISTORY_CNT> vector_history = {};
     int vector_history_index = 0;
     float smoothed_last_state = 0.f;
 
@@ -66,7 +82,8 @@ public:
     float override_state = 0.5f;
 
     explicit Analog(std::string name) : name(std::move(name)) {
-        vector_history.fill({0.0, 0.f, 0.f});
+    };
+    explicit Analog(std::string name, GameAPI::Analogs::AnalogType type) : name(std::move(name)), type(type) {
     };
 
     std::string getDisplayString(rawinput::RawInputManager* manager);
@@ -214,4 +231,12 @@ public:
     inline std::queue<float> &getDelayBuffer() {
         return this->delay_buffer;
     }
+
+    inline GameAPI::Analogs::AnalogType getType() const {
+        return this->type;
+    }
+
+    inline void setType(GameAPI::Analogs::AnalogType type) {
+        this->type = type;
+    }
 };