[webdriver] Move Webdriver to ServoShell (#36714)

Moving `webdriver` to `servoshell`:

- Let `servoshell` manage lifecycle of `webdriver`
- One by one, move the handling of webdriver commands from
`constellation` to `embedder`

Partially fix: https://github.com/servo/servo/issues/37370
Partially fix webdriver test timeout with `no_top_browsing_context`

cc: @xiaochengh

---------

Signed-off-by: batu_hoang <longvatrong111@gmail.com>

components/shared/embedder/lib.rs

@@ -372,6 +372,7 @@ pub enum EmbedderMsg {
         JavaScriptEvaluationId,
         Result<JSValue, JavaScriptEvaluationError>,
     ),
+    WebDriverCommand(WebDriverCommandMsg),
 }
 
 impl Debug for EmbedderMsg {