rawinput: remove experimental analog features (delay and relative axis mode) (#668)

## Link to GitHub Issue or related Pull Request, if one exists
Related to #181 

## Description of change
This PR removes two features marked as "experimental" for analog axis -
`Delay` and `Relative Axis`.

They have been in spice as experimental option for almost 2 years.. but
they have a fundamental problem of being tied to how often the analog is
polled. Not just how often the game's I/O emulation code polls it, but
literally any source (spice API, overlay, etc).

For `Delay`, the only real usage I'm aware of is for #181 which is
delaying IIDX turntable input. For this, I will follow up with a
separate PR that adds back the delay option specifically for IIDX.

For `Relative Axis` - I'm not quite sure if any one actually uses this.
This could be implemented per-game if some game demands it. Polaris
Chord already has one, for example.

## Testing

src/spice2x/overlay/windows/controller_presets.h

@@ -71,8 +71,6 @@ namespace overlay::windows {
         bool invert = false;
         bool smoothing = false;
         int multiplier = 1;
-        bool relative_mode = false;
-        int delay_buffer_depth = 0;
 
         bool is_device() const { return !device_identifier.empty(); }
         bool is_unbound() const { return device_identifier.empty() && index == 0xFF; }
@@ -89,8 +87,6 @@ namespace overlay::windows {
             invert = a.getInvert();
             smoothing = a.getSmoothing();
             multiplier = a.getMultiplier();
-            relative_mode = a.isRelativeMode();
-            delay_buffer_depth = a.getDelayBufferDepth();
         }
     };