Be smarter about running integration commands

[See original issue on GitLab](https://gitlab.com/BuildStream/buildstream/-/issues/464)
In GitLab by [[Gitlab user @TheRealMichaelCatanzaro]](https://gitlab.com/TheRealMichaelCatanzaro) on Jul 9, 2018, 10:49

Currently all integration commands run when building every module. This is often unnecessary. E.g. there is no value in running 'update-ca-certificates' except right after building the ca-certificates package. [[Gitlab user @tristanvb]](https://gitlab.com/tristanvb) suggests we need domains for integration commands to know when it's necessary. Build integration or runtime integration has different requirements. If we split it, Tristan thinks we could cut the time required by ~80%.

Start with the linked GitLab issue and trace how integration commands are currently selected and run when building modules. Define the proposed domains for integration commands, including build-time and runtime requirements, and verify that commands run only for relevant modules while preserving required integration behavior.

Written by the indexing model from the issue text.