Remove current node implementation

[rosahbruno]

To properly configure Glean.js to be only synchronous, we are going to drop the existing support for node first. The other PR I am working on #1808 is rebuilding the Glean internals. To be able to do this, we first need to remove QT, node, and the webext implementations.

By removing these first, we are going to be able to build new platforms/packages for each in a more reusable way that scales nicer than what we are currently doing.

The reason we are doing this now and then going to put it back in is because to be able to drop the async/sync/shared file structure, we need to remove all the platforms except for web.

Pull Request checklist

• Quality: Make sure this PR builds and runs cleanly.
  • Inside the glean/ folder, run:
    • npm run test Runs all tests
    • npm run lint Runs all linters
• Tests: This PR includes thorough tests or an explanation of why it does not
• Changelog: This PR includes a changelog entry to CHANGELOG.md or an explanation of why it does not need one
• Documentation: This PR includes documentation changes, an explanation of why it does not need that or a follow-up bug has been filed to do that work
  • Documentation should be added to The Glean Book when making changes to Glean's user facing API
    • When changes to the Glean Book are necessary, link to the corresponding PR on the mozilla/glean repository
  • Documentation should be added to the Glean.js developer documentation when making internal code changes

[Dexterp37]

I'm ok with moving forward with this, as discussed during our workweek.

We should make sure that this has no impact on the one consumer we have (Treeherder). @badboy checked and it seems this is just UI.

We should probably merge this, cut a new alpha release and see.