Prompt-less upload from trusted hosts

[maleadt]

It would be nice if we could re-use the upload code here from PkgEval instead of rolling our own and uploading to the Nanosoldier S3 bucket. Similarly, we may want to use --bug-report=... as part of CI (package CI, or even Base Julia CI). In both cases we don't want BugReporting.jl to prompt for GH auth. We could avoid this by supporting a whitelist of hosts, or by using a GITHUB_TOKEN as specified in the environment. Thoughts, @staticfloat?