[WebDriver] Fully implement "switch to (parent) frame" (#37685)

1. Separate the handling of ["switch to parent
frame"](https://w3c.github.io/webdriver/#switch-to-parent-frame) from
the rest as the processing is a bit different
2. Implement "Select frame by 16-bits numbered ID" for ["switch to
frame"](https://w3c.github.io/webdriver/#switch-to-frame)
3. Implement other missing steps

Testing: All WebDriver Conformance test with new passing cases

---------

Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>

components/shared/embedder/webdriver.rs

@@ -198,6 +198,7 @@ pub enum WebDriverScriptCommand {
         WebDriverFrameId,
         IpcSender<Result<BrowsingContextId, ErrorStatus>>,
     ),
+    GetParentFrameId(IpcSender<Result<BrowsingContextId, ErrorStatus>>),
     GetUrl(IpcSender<ServoUrl>),
     GetPageSource(IpcSender<Result<String, ErrorStatus>>),
     IsEnabled(String, IpcSender<Result<bool, ErrorStatus>>),
@@ -240,7 +241,6 @@ pub type WebDriverJSResult = Result<WebDriverJSValue, WebDriverJSError>;
 pub enum WebDriverFrameId {
     Short(u16),
     Element(String),
-    Parent,
 }
 
 #[derive(Debug, Deserialize, Serialize)]