Default log behaviour should be useful, easy-to-read with maximum information and minimal waste lines

[See original issue on GitLab](https://gitlab.com/BuildStream/buildstream/-/issues/505)
In GitLab by [[Gitlab user @devcurmudgeon]](https://gitlab.com/devcurmudgeon) on Jul 25, 2018, 12:54

This is a generic point which I'm hoping can be considered/discussed separately from specific issues I'm about to raise on (default) logs that bst currently generates.

In part this is because it may be that some of the following issues could lead to "that can be done via configuration. closed" which may or may not be a good outcome, depending on whether the default is 'better' than the non-default configuration.

Start with the linked GitLab issue and its discussion of BuildStream's default logs. Review the specific default-log issues referenced there and determine whether the requested behavior belongs in the defaults or configuration. Done means an agreed default that is readable, information-rich, and avoids unnecessary lines.

Written by the indexing model from the issue text.