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/cfg/controller_presets.cpp

@@ -69,8 +69,6 @@ namespace overlay::windows {
         el->SetAttribute("invert", analog.invert);
         el->SetAttribute("smoothing", analog.smoothing);
         el->SetAttribute("multiplier", analog.multiplier);
-        el->SetAttribute("relative", analog.relative_mode);
-        el->SetAttribute("delay", analog.delay_buffer_depth);
         parent->InsertEndChild(el);
     }
 
@@ -92,8 +90,6 @@ namespace overlay::windows {
         el->QueryBoolAttribute("invert", &a.invert);
         el->QueryBoolAttribute("smoothing", &a.smoothing);
         el->QueryIntAttribute("multiplier", &a.multiplier);
-        el->QueryBoolAttribute("relative", &a.relative_mode);
-        el->QueryIntAttribute("delay", &a.delay_buffer_depth);
 
         return a;
     }