Removes the checked-in @berry/pnpify & @berry/builder

[arcanis]

This PR removes the checked-in versions of @berry/pnpify and @berry/builder that are stored within the repository. We previously needed them in order to build Yarn (we needed), but I found a way to do this using ts-node to add TypeScript support at runtime. The key was:

• ts-node supports an option called transpileOnly. This avoids the typechecking errors that would happen when running pnpify from its TS sources because TypeScript wouldn't be able to find the modules.

• Disabling the typechecking this way isn't a problem because we use pnpify to build itself (by calling tsc), meaning that the typecheck will be effectively run - just slightly later in the process.

• I've implemented a publishConfig.bin property which allows us to use different binaries locally than the ones used when the package gets downloaded from the registry. This makes it possible to auto-register ts-node locally, but just run the regular binary in all other cases. This avoid having to complicate our scripts to bootstrap ts-node or similar.

@Vlasenko Did you consider using ts-node when you implemented PnPify? I'm curious if I'm forgetting some edge cases that would make this strategy crumble 😄

[arcanis]

In term of performances, running ./scripts/update-local.sh yielded almost no performance change between this branch and master (45s in both cases), which I find slightly surprising 🤔

[arcanis]

Merging to fix the pnp hook build

[larixer]

@arcanis Nope, I didn't consider ts-node when implemented PnPify.

Cool, thats much easier, I love it!