Convert to ESM and rely on a single lwc package

[nolanlawson]

This would be the first step to achieving #349. We should not have multiple @lwc/* package dependencies, but rather a top-level lwc dependency, and do our imports like this:

import compiler from 'lwc/compiler'

This requires converting from CommonJS to ESM.

[nolanlawson]

This would require our own consumers to use ESM. Although maybe it will be possible in future versions of Node: https://joyeecheung.github.io/blog/2024/03/18/require-esm-in-node-js/

[nolanlawson]

After discussion in #349 I'm not sure how valuable this would be.