script: Lazy init and reuse const BOOLEAN_ATTRIBUTES (#38423)

Follow up of  #38401.
- The constant String array was recreated for every invocation. Chromium
store this as a global const.
https://source.chromium.org/chromium/chromium/src/+/main:chrome/test/chromedriver/element_commands.cc;l=48-94?q=chrome%2Ftest%2Fchromedriver%2Felement_commands.cc
We now use static `LazyLock` to lazy init and avoid recreation.
- Clean up some comments

Testing: Just refactor.

---------

Signed-off-by: Euclid Ye <euclid.ye@huawei.com>

components/script/webdriver_handlers.rs

@@ -1584,7 +1584,6 @@ pub(crate) fn handle_get_attribute(
         .send(
             get_known_element(documents, pipeline, node_id).map(|element| {
                 if is_boolean_attribute(&name) {
-                    // element.get_attribute_by_name(DOMString::from(name)).map(|_| String::from("true"))
                     if element.HasAttribute(DOMString::from(name)) {
                         Some(String::from("true"))
                     } else {