Getting current channel info was kind of annoying via RPC. Two
functions had to be called:
1. `nvim_get_api_info` which returns `[channel_id, meta_data]`.
- This results in `channel_id = api.nvim_get_api_info()[0]`.
- Here the meta_data is sent but never used.
2. Finally call `nvim_get_chan_info(channel_id)`.
This commit reduces the need for `nvim_get_api_info` as passing 0
returns current channel info.
b162adbb7c
