Set virtual grain in Podman systemd container

[tacerus]

What does this PR do?

Correctly handle the systemd-detect-virt output to identify a Podman
container running systemd as what it is instead of as a physical machine.

What issues does this PR fix or reference?

Fixes #67733

Previous Behavior

# systemd-detect-virt
podman

# salt-call --local grains.get virtual
local:
    physical

New Behavior

# systemd-detect-virt
podman

# salt-call --local grains.get virtual
local:
    container

Merge requirements satisfied?

[NOTICE] Bug fixes or features added to Salt require tests.

• Docs
• Changelog - https://docs.saltproject.io/en/master/topics/development/changelog.html
• Tests written/updated

Commits signed with GPG?

Yes

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PR Guidelines.

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[tacerus]

Rebased onto 3006.x as per request in #67733 (comment).

[dwoz]

The pre-commit failure needs to be addressed: https://github.com/saltstack/salt/actions/runs/13425907781/job/37510729265?pr=67734

[tacerus]

Hi @dwoz, thanks, I repaired it, however there was a conflict with 3006.x now because 1d4c12e wrote to changelog/67733.fixed.md even though #67733 is (from what I can tell) my issue, going by the PR introducing it (#67723) I think they meant #67722 instead, hence I overwrote the changelog file for my issue and moved theirs, hope that is fine.

[tacerus]

Seems the changelog file was repaired via 3b40940 in the meanwhile, so I rebased mine again.

[dmurphy18]

@tacerus Sorry about the mistake with the changelog file, fixed it, and thanks for the PR, had just setup test environment when my attention was drawn to your PR

[tacerus]

Ah, no worries. :)