For dbt core cli, recommend using typer completions, and improve completions

[joshuataylor]

Cross posting here for more eyeballs..

There is the https://github.com/dbt-labs/dbt-completion.bash project, which provides completions for bash/zsh.

However, typer offers CLI completions via _DBT_COMPLETE=zsh_source dbt.

It'll be great to perhaps use typer as a base (though slow), and then add the functionality that the dbt-completion.bash work does - (fast) model completions.

Issue here: dbt-labs/dbt-completion.bash#28