Volar-ized Glint Roadmap

Overview

This roadmap absorbs the contents of the now-closed Language Tooling RFC.

Now that the initial Volar Refactor PR has been merged, there a number of next steps to pursue before Glint 2.0 is ready for primetime.

[ ] Fix test suite, all green tests, via test.skip() (and add to this issue for any remaining feature TODOs)
[ ] re-enable lints in CI
[ ] Figure out how to resolve conflicts/overlapping with vsc-ember-syntax https://github.com/lifeart/vsc-ember-syntax/issues/72
- I need to review how/why I inlined portions of that addon into this branch; I believe it's because otherwise Glint/Volar can't determine a language ID for .gts files
[ ] get all {{ @glint-expect-error }} and related directives working
[ ] Support for .gjs (and passing tests)
[ ] Support for .hbs and companion files
[ ] constrain data objects on nested embedded codes https://discord.com/channels/1192759067815464990/1252021970443440128/1252298644695158874