This reverts commit 3f54ef7525ed357ce64bf375ef7ce3d70a52ba61.
The filesystem layout used by pnpm means that a nesting of 2
directories deep is used in the wild and must remain.
The sharp.node shared library should now always end up being
nested either 3 subdirectories deep into the package root or exist
within same namespace of the node_modules tree.
If you want to build sharp from source against a globally-installed
libvips then you will now need to add both node-addon-api and
node-gyp to the dependencies section of your package.json file.
The binding.gyp file is "hidden" inside the src directory to
prevent various build and package manager tooling from assuming
that everyone is going to build from source every time.
