Remove ./helpers/esm exports from @babel/runtime and drop Node.js 13.0-13.1

[nicolo-ribaudo]

Q	A
Fixed Issues?	Fixes #1, Fixes #2
Patch: Bug Fix?
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	Yes
Documentation PR Link
Any Dependency Changes?
License	MIT

They are not actually needed anymore, given that we use exports with an import condition. They are there just because Babel emitted /esm/ imports when using useESModule: true, before that package.json#exports was a thing.

This PR also simplify the conditions object, and as a side effects drops support for Node.js 13.0 and 13.1. In general I'd like to keep @babel/runtime as maximally compatible as possible, but this should be fine.

Now package.json is like this:

  "exports": {
    "./helpers/AsyncGenerator": {
      "node": "./helpers/AsyncGenerator.js",
      "import": "./helpers/esm/AsyncGenerator.js",
      "default": "./helpers/AsyncGenerator.js"
    },
    "./helpers/OverloadYield": {
      "node": "./helpers/OverloadYield.js",
      "import": "./helpers/esm/OverloadYield.js",
      "default": "./helpers/OverloadYield.js"
    },

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/56506

[liuxingbaoyu]

Is the node entry still necessary?

[nicolo-ribaudo]

Is the node entry still necessary?

Yes, because some helpers should only be loaded once if possible (for example, _temporalUndefined) if possible.