Closes  [#20574](https://github.com/zed-industries/zed/issues/20574)

Release Notes:

- Replaced editor action editor::AcceptPartialEditPrediction with
editor::AcceptNextLineEditPrediction and
editor::AcceptNextWordEditPrediction

Tested manually on windows, attaching screen cap.
https://github.com/user-attachments/assets/fea04499-fd16-4b7d-a6aa-3661bb85cf4f

Updated existing test for accepting word prediction in copilot - it is
already marked as flaky, not sure what to do about it and I'm not really
confident creating new one without a working example.

Added migration of keymaps and new defaults for windows, linux, macos in
defaults and in cursor.

This should alleviate
[#21645](https://github.com/zed-industries/zed/issues/21645)
I used some work done in stale PR
https://github.com/zed-industries/zed/pull/25274, hopefully this one
makes it through!

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Co-authored-by: Agus Zubiaga <agus@zed.dev>