This change formats log messages the same way that Node.js does
in its console.log/error APIs. This ensures, for example, that
errors have their stack printed if present, and switches over to
just printing the error directly rather than manually toStringing it.
This exposes the existing runtime logging functionality in a way meant
for 3rd-parties to consume. This can be useful if we want to introduce
debug logging, warnings, or other things, that fit nicely with the
Pulumi CLI and overall developer workflow.
