build: install built packages

In many use cases (especially packaging tests/CI) it's desirable to install native package created by apkg build.

Original intention was like this:

apkg build | apkg install -C -F -

But it turns out apkg build may produce stdout noise from installation of build depends so this doesn't always work.

• Fix all external tool invocations across apkg to not spam stdout. If seeing output is really desire outside of error, extend run wrapper with ability to pipe stdout to stderr.
• Extend tests to ensure apkg build | apkg install -F - always works.