CurlStimulus: take axis and center directly from the Region

by taking more from the region, we'll be able to reuse common code
and also make this more testable

crates/applications/sr_latch/src/main.rs

@@ -84,8 +84,6 @@ fn main() {
         driver.add_stimulus(CurlStimulus::new(
             region.clone(),
             wave.clone(),
-            region.center(),
-            region.axis()
         ));
     };