Add minimum Kubernetes version supported

Add the minimum Kubernetes version supported to the application metadata
file.

The minimum Kubernetes version is set to 1.24.4 and should be changed
accordingly for future application updates.

The "supported_k8s_version:minimum" field is optional but it will become
mandatory in the near future.

This also contains a fix to properly trigger the Tox metadata checks.

Test Plan
PASS: build-pkgs && build-image
PASS: Apply application

Story: 2010929
Task: 49494

Change-Id: I946413552b24aa43cc17aff1df6f824ceb57395f
Signed-off-by: Igor Soares <Igor.PiresSoares@windriver.com>

.zuul.yaml

@@ -50,8 +50,6 @@
       - starlingx/update
       - starlingx/utilities
       - starlingx/root
-    files:
-      - python3-k8sapp-istio/*
     vars:
       tox_envlist: metadata
       tox_extra_args: -c python3-k8sapp-istio/k8sapp_istio/tox.ini

stx-istio-helm/stx-istio-helm/files/metadata.yaml

@@ -5,4 +5,7 @@ app_version: APP_REPLACE_VERSION
 helm_repo: HELM_REPLACE_REPO
 
 upgrades:
-  auto_update: true
+  auto_update: true
+
+supported_k8s_version:
+  minimum: 1.24.4