Fix ORAS repo auth

[isc-dchui]

Description

• Fixes Unable to connect to Github Container Registry #1130
• Addresses a few gaps in the ORAS repo implementation:
  • Fixes the auth flow for checking availability of repository
  • Repo URL no longer requires scheme since the default is often scheme-less, e.g. ghcr.io vs https://ghcr.io
  • Adds an "Authenticated?" line to the repo display for ORAS repos
  • Adds implementation of bearer token exchange for probing of credentials because the ORAS library does not support timeouts

Testing

Tested this manually:
First created a PAT with appropriate scopes (https://docs.github.com/en/packages/working-with-a-github-packages-registry/working-with-the-container-registry).
Then configured using this IPM line: repo -o -n github -url ghcr.io -namespace <GitHub-username> -username <GitHub-username> -password <PAT>.
Was able to install and publish modules to and from the repo.

Added some unit tests and removed the redundant preexisting test because 1) it's an integration test not a unit test, and 2) everything it tests is already covered elsewhere.

Checklist

• This branch has the latest changes from the main branch rebased or merged.
• Changelog entry added.
• Unit (zpm test -only) and integration tests (zpm verify -only) pass.
• Style matches the style guide in the contributing guide.
• Documentation has been/will be updated
  • I'll add an extra section to the wiki
• Pull request correctly renders in the "Preview" tab.