tests: Refactors container image usage

Currently, the cri-integration tests do not work on Windows due to various reasons.
One of the reasons is because all the tests are using Linux-specific images. This
commit refactors the image pulling / usage in the cri-integration tests, making it
easier to update, and easier to configure the a custom registry to pull those images
from.

For Windows runs, custom registries can be created, which will also contain Windows
images, and the cri-integration tests can be configured to use those registries by
specifying the "--image-list" argument, a TOML file which will contain an alternative
mapping of the default images.

Signed-off-by: Claudiu Belu <cbelu@cloudbasesolutions.com>

script/test/cri-integration.sh

@@ -37,7 +37,8 @@ sudo PATH=${PATH} bin/cri-integration.test --test.run="${FOCUS}" --test.v \
   --cri-endpoint=${CONTAINERD_SOCK} \
   --cri-root=${CRI_ROOT} \
   --runtime-handler=${RUNTIME} \
-  --containerd-bin=${CONTAINERD_BIN}
+  --containerd-bin=${CONTAINERD_BIN} \
+  --image-list="${TEST_IMAGE_LIST:-}"
 
 test_exit_code=$?