This PR fixes the following edge case:
- `const oldPromise = world.puppeteerUtil`.
- setContext occurs but context is immediately destroyed, i.e.
`world.#puppeteerUtil === oldPromise` is not resolved.
- clearContext occurs due to destruction, i.e. `world.#puppeteerUtil` is
replaced (`world.#puppeteerUtil !== oldPromise`).
- `oldPromise` never resolves.
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.
