Errors are printed to STDOUT instead of STDERR

[KevinFCormier]

All the scripts seem to use printf to print errors to stdout before exiting. For example:

https://github.com/open-cluster-management/lifeguard/blob/main/clusterpools/apply.sh#L38

printf "${RED}Unable to create AWS Credentials Secret. See above message for errors.  Exiting."
exit 3

I think as a standard practice, errors should be printed to stderr.

I am invoking some of these scripts from other scripts, so in some cases I need to suppress the output or process the output for logging, etc. This made it difficult to debug because execution was stopped when your script exited with an error code, but I did not have the benefit of seeing the output saying that I was missing gsed.

I am happy to create a PR for this, but I wanted to check first if you are in agreement with this!