feat(permissions): allow npm packages to read their own data files
npm packages frequently ship data files (JSON vocabularies, wasm
binaries, lookup tables, etc.) and read them at runtime via `fs`. Until
now this required the user to pass `--allow-read`, even though the
package code itself was already loaded and executed without an explicit
read grant.
Grant implicit read access to the local `node_modules` directory and the
global npm cache directory so that npm packages can read their own
bundled data files without any permission flags. Only read access is
granted implicitly; writes still require `--allow-write`, and reads of
files outside those directories still require `--allow-read`.
Closes #18607
Co-Authored-By: Divy Srivastava <me@littledivy.com>
