fix: offset_encoding is required now in make_position_params

[rockyzhang24]

Adapt to the upstream change neovim/neovim@629483e to get rid of the warning message "warning: offset_encoding is required, using the offset_encoding from the first client".

Since the commit neovim/neovim@2dcbfe7, params in buf_request can accept a function that takes the client as a parameter. So instead of sending the same params to all servers, the params with correct offset_encoding will send to each single server.

[rockyzhang24]

I just realized that the has function for checking version numbers returns 0 or 1 instead of a boolean. I’ve fixed it, and everything should be fine now. It’s ready to be merged.

[Conni2461]

thanks for the contribution :) i left a couple of nits