chore(cli): export from index.js (#18999)

As a preparation for bundling, extract the entire CLI script into a function and export it from `index.js`. 
This will allow the future bundler to simply bundle `index.js` and preserve all current exports for programatic usage. 

Note that deep imports will still not work after bundling, but thats ok since those imports are considered private and should not have been used. 

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Author: iliapolo