[master] Use relenv.fetch to download tarball

[Akm0d]

What does this PR do?

This PR updates the salt-ssh --relenv functionality to change the source from which the Salt Onedir package is downloaded. Instead of using salt.utils.http to fetch packages from repo.saltproject.com, the logic is updated to leverage relenv.fetch to pull the package from the new Artifactory location. This transition ensures that the retrieval process remains consistent and up-to-date with the newly hosted package locations.

What issues does this PR fix or reference?

Fixes #67010

Previous Behavior

• Utilized salt.utils.http to download the Salt Onedir package from repo.saltproject.com.

New Behavior

• Uses relenv.fetch to download the Salt Onedir package from the new Artifactory location. This abstracts URL handling and ensures download paths align with updated infrastructure.

Merge requirements satisfied?

• Documentation: Updates have been made to reflect changes in the URL source.
• Changelog: Please see the changelog for more information on this update: Changelog.
• Tests written/updated: Tests have been adjusted to confirm the new download functionality works as expected.

Commits signed with GPG?

Yes

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