This PR combines the publishing workflows for npm packages and Docker.
It also fixes an issue where multiple tags would trigger publishing all
packages.
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.
This PR starts the monorepo migrations as per
https://github.com/puppeteer/puppeteer/issues/8922. To scope migrations,
we are only moving the `testserver` into a separate package. Further
migrations will come later.
