feat: NVSHAS-9502 create standalone Dockerfile

1. Provide cross platform/standalone Dockerfile
2. Release.yml to publish SLSA-capable artifacts
3. Provide build target, test-image, build-image and push-image to sync
   with rancher.
4. Upgrade to BCI 15.6

.github/workflows/release.yml

@@ -38,6 +38,7 @@ jobs:
       with:
         push-to-public: true
         push-to-prime: false
+        make-target: push-image
         image: prometheus-exporter
         tag: ${{ env.TAG }}
         platforms: linux/amd64,linux/arm64
@@ -51,6 +52,7 @@ jobs:
       with:
         push-to-public: false
         push-to-prime: true
+        make-target: push-rancher-image
         image: neuvector-prometheus-exporter
         tag: ${{ env.TAG }}
         platforms: linux/amd64,linux/arm64

Makefile

@@ -61,6 +61,12 @@ build-image: buildx-machine ## build (and load) the container image targeting th
 
 
 push-image: buildx-machine
+	$(IMAGE_BUILDER) build -f package/Dockerfile \
+		--builder $(MACHINE) $(IMAGE_ARGS) $(IID_FILE_FLAG) $(BUILDX_ARGS) \
+		--build-arg VERSION=$(VERSION) --build-arg COMMIT=$(COMMIT) --platform=$(TARGET_PLATFORMS) -t "$(REPO)/prometheus-exporter:$(TAG)" --push .
+	@echo "Pushed $(IMAGE)"
+
+push-rancher-image: buildx-machine
 	$(IMAGE_BUILDER) build -f package/Dockerfile \
 		--builder $(MACHINE) $(IMAGE_ARGS) $(IID_FILE_FLAG) $(BUILDX_ARGS) \
 		--build-arg VERSION=$(VERSION) --build-arg COMMIT=$(COMMIT) --platform=$(TARGET_PLATFORMS) -t "$(REPO)/neuvector-prometheus-exporter:$(TAG)" --push .