Migrate to ropey 2

[archseer]

Requires helix-editor/regex-cursor#6

[the-mikedavis]

I wonder if we can gate v2 behind a feature flag? I don't want to break other tree-house consumers to introduce support for ropey v2 if we can avoid it. If not, we could make use a new minor to add ropey v2 support and backport any fixes we make to the previous minor, for better compatibility.

cc @hadronized we will eventually want to migrate tree-house (as well as all of Helix) towards ropey v2 and then cessen will release ropey v2, FYI.