Support Podman for mocking Lambda (#3702)

* Support Podman for mocking Lambda

Podman supports all Docker APIs used in moto since version 3.0. Note
that Podman requires pulling the image before creating a container
using a fully-qualified image name (e.g., "docker.io/library/busybox"
instead of "busybox").

Test plan:
$ podman system service -t 0
$ DOCKER_HOST="unix://$XDG_RUNTIME_DIR/podman/podman.sock" pytest

Fixes https://github.com/spulec/moto/issues/3276

* Run black

* Python 2 compatibility

* Address review comments and improve parse_image_ref

tests/test_utilities/test_docker_utilities.py

@@ -0,0 +1,31 @@
+import sure
+import pytest
+
+from moto.utilities.docker_utilities import parse_image_ref
+
+
+@pytest.mark.parametrize(
+    "image_name,expected",
+    [
+        ("python", ("docker.io/library/python", "latest")),
+        ("python:3.9", ("docker.io/library/python", "3.9")),
+        ("docker.io/python", ("docker.io/library/python", "latest")),
+        ("localhost/foobar", ("localhost/foobar", "latest")),
+        ("lambci/lambda:python2.7", ("docker.io/lambci/lambda", "python2.7")),
+        (
+            "gcr.io/google.com/cloudsdktool/cloud-sdk",
+            ("gcr.io/google.com/cloudsdktool/cloud-sdk", "latest"),
+        ),
+    ],
+)
+def test_parse_image_ref(image_name, expected):
+    expected.should.be.equal(parse_image_ref(image_name))
+
+
+def test_parse_image_ref_default_container_registry(monkeypatch):
+    import moto.settings
+
+    monkeypatch.setattr(moto.settings, "DEFAULT_CONTAINER_REGISTRY", "quay.io")
+    ("quay.io/centos/centos", "latest").should.be.equal(
+        parse_image_ref("centos/centos")
+    )