Previously, every base derived from the IStreamingReporter had
its own `IConfig const* m_config` member, so this just centralizes
the handling thereof.

Part of #2061

The previous commit made it so that the `IConfig` is stored in
`IStreamingReporter` and thus always available.

Also generalized the implementations to write to the provided
output stream, which will be required for the follow up changes,
where the listings should happen to the location user asked for
by specifying the `-o` flag.

Also added tests for the default implementations of list* reporter
helpers.

Closes #2061