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.
Partial fix for https://github.com/microsoft/playwright/issues/6319
After this fix, the following scenario won't leak and the context state
(cookies, storage, etc) can be reused by the new page sessions:
```js
for (let i = 0; i < 1000; ++i) {
const page = await context.newPage();
await page.goto('...');
await page.close('...');
}
```
- Never use open shadow root for highlight. This messes up
our selectors that accidentally match internal preview elements.
- Remove failing electron test that we do not care about.
- Skip `channels.spec.ts` in non-default mode.
Previously, we only validated/converted on the way to the server,
but not from the server.
Validating both ways catches issues earlier, and allows us to
perform automatic conversions, for example only converting
buffers to base64 when sending over wire.
