REFACTOR(argocd): separate image-updater manifests

- Move ExternalSecrets to image-updater-manifests folder
- Add manifests source to image-updater Application
- Remove unnecessary ignoreDifferences from argocd

argocd/argocd.yaml

@@ -53,16 +53,3 @@ spec:
       name: argocd-initial-admin-secret
       jsonPointers:
         - /data
-    - group: external-secrets.io
-      kind: ExternalSecret
-      jsonPointers:
-        - /spec/data/0/remoteRef/conversionStrategy
-        - /spec/data/0/remoteRef/decodingStrategy
-        - /spec/data/0/remoteRef/metadataPolicy
-        - /spec/data/1/remoteRef/conversionStrategy
-        - /spec/data/1/remoteRef/decodingStrategy
-        - /spec/data/1/remoteRef/metadataPolicy
-    - group: monitoring.coreos.com
-      kind: ServiceMonitor
-      jsonPointers:
-        - /spec/endpoints/0/metricRelabelings