**What kind of change does this PR introduce?**
I have browsers pool in some cloud. I want that only users with access
will be able to connect to them. So they must provide token through
headers. But puppeteer does not allow to send headers when connected to
browser by ws connection. So I added this feature.
Closes#7218
This PR moves the puppeteer source code into separate mono-repo packages:
- `puppeteer` and `puppeteer-core` are now separated into their own
packages.
- `puppeteer-core` has a new exports called `puppeteer-core/internal`
for internal usage.
Tests and various tools have been updated to accommodate the migration.
