V3

[moonglum]

This PR introduces a few breaking changes. We collect them to have a nice, clean v3 - dropping some things that drag us down along the way.

• We drop Virtual entirely. It was not used, and adds significant complexity

  • This allows us to collapse the bundle inheritancy hierarchy

• We drop support for custom extensions

  • I don't think we should have even included it in the first place, I think it is a violation of the faucet philosophy of only supporting "standard code"
  • The file extensions for TypeScript & JSX are added automatically

• We make ESM the new default format (previously it was IIFE). It is a breaking change, but a very necessary one.

• Remove an old unused test util and a really old deprecation warning

• We drop support for Node 14

• [x] Use ES2015 Syntax in generated code

[FND]

FYI: In an effort to refamiliarize myself with this, I've reviewed every commit here and made some minor changes (mostly tweaking and amending commit messages).

We'll now need to update our test suite to account for latest transpilation changes, but there are also dependencies to be updated (it might make sense to do the latter first).