This PR allows users to `--export`, `--export-secret`, or both to export GPG keys
from Spack. The docs are updated that include a warning that this usually does not
need to be done.
This addresses an issue brought up in slack, and also represented in #14721.
Signed-off-by: vsoch <vsoch@users.noreply.github.com>
Co-authored-by: vsoch <vsoch@users.noreply.github.com>