Standardize Command Output Logging Formats

https://github.com/haskell/cabal/pull/8292#discussion_r922887939 says:

> It seems to me that the single-line space clearing done after the command output is finished in terminal is currently standard in master for a few commands, including init. Its removal introduces inconsistency at least in this pr. However, functions like sdist introduce 2 newlines upon failure, and others none at all upon success. I think this warrants some discussion.

This makes sense. If there are no objections, let's standardize on "single-line space clearing done after the command output is finished in terminal", prescribe it in CONTRIBUTING.md and chase down any misbehaving code (perhaps in separate numerous tickets and/or PRs, as long as there is one master ticket kept open until all ducks are in a row).

Start with the linked pull request discussion and inspect CONTRIBUTING.md to understand the proposed single-line space-clearing convention. Identify command implementations with inconsistent output behavior, then update the guidance and coordinate the related fixes so successful and failed commands follow the chosen standard.

Written by the indexing model from the issue text.