Add podman

[mbargull]

Checklist

• Title of this PR is meaningful: e.g. "Adding my_nifty_package", not "updated meta.yaml"
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[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipes/podman) and found it was in an excellent condition.

[mbargull]

I intend to

• not upstream 0001-Add-missing-defines-for-CentOS-6.patch
  IMO, we (conda-forge) should update to cos7 in the foreseeable future.
  And I don't want to burden upstream with temporarily adding these patches.
• upstream 0002-Use-CPP-CC-and-flags-in-dep-check-scripts.patch. done in Use CPP, CC and flags in dep check scripts containers/podman#8260
• work with upstream on how we can support the Conda use case with something less ugly than
  0003-Allow-relative-paths-for-system-config-files.patch.
  (Upstream was very forthcoming when @epruesse packaged skopeo, hence I believe we can work this out.)
  The patch works and I intend to maintain it until we have upstream support, but it's quite hacky and ideally we'd
  have something more robust that doesn't involve FallbackToPathRelativeToExe calls in random places etc.
  ref: Support for custom/relocatable install prefixes (Conda packages) containers/common#346