neovim: migrate to neovim's new remote plugin design

[fidgetingbits]

I'm not sure yet what we'll have to change, but https://github.com/neovim/neovim/issues/27949 is tracking development that will rework how remote plugins work in neovim, so likely will affect how the node function registration works.

Once we change it will also mean we have to specify whatever version of neovim ends up supporting the new way (currently planned for 0.11) will become a requirement for using cursorless.nvim.