Fix canonical image ref resolution

Adds a new util to reliably resolve canonical reference to the image.

Previously in release scripts we were using `docker inspect`
which seems to sort .RepoDigests and it makes selection of the
correct digest difficult because platform-specific digest can
appear at a different index depending on the digests in the list.

Signed-off-by: Mikalai Radchuk <[email protected]>

Author: Mikalai Radchuk

Diff for: Makefile

@@ -312,17 +312,17 @@ pull-opm:
 
 .PHONY: package
 package: $(YQ) $(HELM) #HELP Package OLM for release
-package: OLM_RELEASE_IMG_REF=$(shell docker inspect --format='{{index .RepoDigests 0}}' $(IMAGE_REPO):$(RELEASE_VERSION))
-package: OPM_IMAGE_REF=$(shell docker inspect --format='{{index .RepoDigests 0}}' $(OPERATOR_REGISTRY_IMAGE))
+package: OLM_RELEASE_IMG_REF=$(shell docker images --format='{{.Digest}}' $(IMAGE_REPO):$(RELEASE_VERSION))
+package: OPM_IMAGE_REF=$(shell docker images --format='{{.Digest}}' $(OPERATOR_REGISTRY_IMAGE))
 package:
 ifndef TARGET
 	$(error TARGET is undefined)
 endif
 ifndef RELEASE_VERSION
 	$(error RELEASE_VERSION is undefined)
 endif
-	@echo "Getting operator registry image"
-	docker pull $(OPERATOR_REGISTRY_IMAGE)
+	@echo "Using OPM image $(OPM_IMAGE_REF)"
+	@echo "Using OLM image $(OLM_RELEASE_IMG_REF)"
 	$(YQ) w -i deploy/$(TARGET)/values.yaml olm.image.ref $(OLM_RELEASE_IMG_REF)
 	$(YQ) w -i deploy/$(TARGET)/values.yaml catalog.image.ref $(OLM_RELEASE_IMG_REF)
 	$(YQ) w -i deploy/$(TARGET)/values.yaml package.image.ref $(OLM_RELEASE_IMG_REF)