This pull request introduces initial support for the WebDriver BiDi protocol in Playwright. The primary goal of this PR is not to fully implement BiDi but to experiment with the current state of the specification and its implementation. We aim to identify the biggest gaps and challenges that need to be addressed before considering BiDi as the main protocol for Playwright.
Instead of having `didClose` based on page creation/destruction and
`didDisconnect` based on session lifetime, we make session lifetime
being managed by the `CRPage`/`FFPage`/`WKPage` instead.
