feat(har): include `WebSocket` in `.har` (#41015)

also include data for each sent/received frame in a custom property `_webSocketMessages` (for more info see <https://developer.chrome.com/blog/new-in-devtools-76#websocket>)

both Chrome and WebKit already capture the `wallTime` for the initial request and a `timestamp` for each subsequent message (i.e. diff the `timestamp` relative to the initial `timestamp` and add the `wallTime` in order to determine the current `wallTime`)

Firefox exposes a walltime `timestamp` for each message directly

fixes <https://github.com/microsoft/playwright/issues/30315>