There's a merged pull request on the void-packages repository

Fish completion
https://github.com/void-linux/void-packages/pull/19562

Description:
According to the [fish docs](https://fishshell.com/docs/current/#where-to-put-completions), third-party software should install to `/usr/share/fish/vendor_completions.d`.

See: #19413 (rustup: remove fish completion) as well

Some cleanups, fixes and xlints were performed along the way