Replace current completion generation package with something else

[obvionaoe]

posener/complete has been abandoned (not updated since 2020) and it clearly has some flaws.

It'd be great if it could be replaced with a solution that tackled the issues presented here:

• cli: auto completion of command arguments hashicorp/terraform#28788
• [cli] Emit shell completions to stdout  hashicorp/terraform#32611

Cobra's shell completions provide some of the required features. Could something like it be implemented?

[obvionaoe]

rsteube/carapace also looks within scope of this issue