This PR removes the deprecated query selector API from the `puppeteer`
instance. Direct imports of the query selector API have also been
deprecated and users are now expected to use the static methods defined
on `Puppeteer`.
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.
