scroll element into view for mouse actions

This works fine with Firefox, and conforms to the spec.

However, Chromium gets confused and clicks on the wrong position. Work
around that for now by keeping our old `ph_mouse()` event synthesizer
for Chromium.

bidi.py

@@ -140,10 +140,6 @@ class WebdriverBidi:
         else:
             raise WebdriverError("timed out waiting for default realm")
 
-        # avoid not seeing elements due to too small window
-        # await self.bidi("browsingContext.setViewport", context=self.top_context,
-        #                 viewport={"width": 1024, "height": 5000})
-
     async def __aenter__(self):
         await self.start_session()
         return self