Prior to this change, NewLogger defaulted to sending logs to os.Stdout.
This change updates the method to accept an io.Writer indicating where
logs should go, so that consumers of the SDK could choose to send logs
to stderr, as that is the more typical IO stream for logs.

This is a temporary commit that changes the NewLogger signature but adds
a NewLoggerToStdout function. The next commit will remove
NewLoggerToStdout (preferring NewLogger(os.Stdout) and update the
referenced version of the log module.

Prior to this change, log.NewLogger() was hardcoded to write to stdout.
This is not always desirable: depending on where the logger is
instantiated, it may need to be associated with a (*cobra.Command)'s out
or err stream, or importers of the SDK may want to send logs to stderr
instead of stdout. Additionally, this removes any ambiguity about where
logs may go, when reading the code.

Finally, this allows an easy migration to defaulting logs to stderr,
should we choose to do that in the future.

There were CI failures due to depending on a mismatched pairing of the
log module and the main SDK module.

I missed this earlier due to the linux build tag.