core: Rename IO::run_once() to IO::step()

The `run_once()` name is just a historical accident. Furthermore, it now
started to appear elsewhere as well, so let's just call it IO::step() as we
should have from the beginning.

bindings/javascript/src/lib.rs

@@ -338,7 +338,7 @@ impl Database {
     #[napi]
     pub fn io_loop_sync(&self) -> Result<()> {
         self.io
-            .run_once()
+            .step()
             .map_err(|e| Error::new(Status::GenericFailure, format!("IO error: {e}")))?;
         Ok(())
     }
@@ -631,7 +631,7 @@ impl Task for IoLoopTask {
     type JsValue = ();
 
     fn compute(&mut self) -> napi::Result<Self::Output> {
-        self.io.run_once().map_err(|e| {
+        self.io.step().map_err(|e| {
             napi::Error::new(napi::Status::GenericFailure, format!("IO error: {e}"))
         })?;
         Ok(())