webdriver: Refactor webdriver session and improve window handles (#38745)

This PR contains 2 parts:

1. Refactor webdriver session.
2. Improve webdriver window handles:
- Webdriver always get window handles from script thread by default.
- If script thread is blocked by user prompt, embedder stores the window
handle before user prompt appears, then webdriver can get window handle
from embedder.

Testing: Clear timeout cause by user prompt blocking script thread:
https://github.com/longvatrong111/servo/actions/runs/17033900026

---------

Signed-off-by: batu_hoang <hoang.binh.trong@huawei.com>
Signed-off-by: batu_hoang <longvatrong111@gmail.com>
Co-authored-by: Euclid Ye <euclid.ye@huawei.com>

components/shared/embedder/webdriver.rs

@@ -156,8 +156,8 @@ pub enum WebDriverCommandMsg {
     FocusWebView(WebViewId, IpcSender<bool>),
     /// Get focused webview. For now, this is only used when start new session.
     GetFocusedWebView(IpcSender<Option<WebViewId>>),
-    /// Get all webviews
-    GetAllWebViews(IpcSender<Result<Vec<WebViewId>, ErrorStatus>>),
+    /// Get webviews state
+    GetAllWebViews(IpcSender<Vec<WebViewId>>),
     /// Check whether top-level browsing context is open.
     IsWebViewOpen(WebViewId, IpcSender<bool>),
     /// Check whether browsing context is open.
@@ -246,7 +246,6 @@ pub enum WebDriverScriptCommand {
     WillSendKeys(String, String, bool, IpcSender<Result<bool, ErrorStatus>>),
     AddLoadStatusSender(WebViewId, IpcSender<WebDriverLoadStatus>),
     RemoveLoadStatusSender(WebViewId),
-    GetWindowHandle(IpcSender<Result<String, ErrorStatus>>),
 }
 
 #[derive(Debug, Deserialize, Serialize)]