This PR adds one LavaMoat background script policy or each build type. It also renames the build system policy directory from `node` to `build-system` to make its purpose more clear. Each build type has the original `policy-override.json` for `main` builds. The `.prettierignore` file has been updated to match the locations of the new auto-generated policy files.
We need to maintain separate policies for each build type because each type will produce different bundles with different internal and external modules.
Co-authored-by: Mark Stacey <markjstacey@gmail.com>
