In #38745, we changed the id of Frame and Window as the result of
`ToString` trait. This PR
- adapts the parsing of frame/window accordingly.
- for frame, return the
[WindowProxy](https://developer.mozilla.org/en-US/docs/Web/API/WindowProxy)
object of the iframe as it's supposed to do.
Testing: `execute_{async_}script/arguments.py`
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Signed-off-by: Euclid Ye <euclid.ye@huawei.com>