Establish baseline webdriver conformance results (#35024)

https://github.com/web-platform-tests/wpt/pull/50041 allows us to start
running the webdriver conformance tests in Servo, which will make it
easier for us to track regressions/improvements in our webdriver server
implementation.

---
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes are part of #15274
- [x] There are tests for these changes

---------

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/webdriver_server/actions.rs

@@ -76,7 +76,7 @@ fn compute_tick_duration(tick_actions: &ActionSequence) -> u64 {
             }
         },
         ActionsType::Key { actions: _ } => (),
-        ActionsType::Wheel { .. } => todo!("Not implemented."),
+        ActionsType::Wheel { .. } => log::error!("not implemented"),
     }
     duration
 }
@@ -176,7 +176,10 @@ impl Handler {
                     }
                 }
             },
-            ActionsType::Wheel { .. } => todo!("Not implemented."),
+            ActionsType::Wheel { .. } => {
+                log::error!("not yet implemented");
+                return Err(ErrorStatus::UnsupportedOperation);
+            },
         }
 
         Ok(())