Ref #6645
Problem:
When a window is resized it takes space from the window right/below first,
and only falls back to the window left/above when there is no more room.
Sometimes a user wants the space to come from a specific direction.
Solution:
Add nvim_win_resize(win, width, height, {anchor}) which resizes a window
with a choosable anchor edge, letting a window grow leftwards or upwards
by taking space from the window to the left or above first. The default
anchor reproduces nvim_win_set_width()/nvim_win_set_height().
Problem: Tests for deprecated highlight API were mixed with current API tests.
Solution: Move them to deprecated_spec.lua and update highlight_spec.lua to use nvim_get_hl.
Problem: `get_option_value` returns caller owned `Object`s but the
corresponding C apis do not marked `FUNC_API_RET_ALLOC` properly.
Solution: add `FUNC_API_RET_ALLOC` to the C apis.
Problem:
The `nvim_notify` API (note: unrelated to `vim.notify()` Lua API) was
not given any real motivation in https://github.com/neovim/neovim/pull/13843
There are, and were, idiomatic and ergonomic alternatives already.
Solution:
Deprecate `nvim_notify`.