[Feature Request] Add a way to load ort-node binaries from an arbitrary path

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### Describe the feature request

When bundling onnxruntime-node as part of a VS Code extension using Webpack, the Node binaries are loaded from `path.join(__dirname, 'node_modules', 'onnxruntime-node', 'bin', 'napi-v3');` (see https://github.com/kimadeline/hello-world-ort-node/pull/2/), so we have to respect this folder structure when copying them over from the `onnxruntime-node` npm package .

It would be helpful if we could specify any path pointing to the `napi-v3` folder, so that we can remove extra layers in the final bundled extension folder.

### Describe scenario use case

This would allow consumers of `onnxruntime-node` to not be constrained by the `node_modules/onnxruntime-node/bin/napi-v3` folder structure when copying ort-node binaries to a destination folder.

Start by tracing how onnxruntime-node resolves binaries under bin/napi-v3 when bundled with Webpack. Define a way for consumers to provide an arbitrary napi-v3 directory, then verify that the VS Code extension scenario works without requiring the node_modules/onnxruntime-node/bin/napi-v3 folder structure.

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