feat(metallb/cloudnative-pg/CI): BREAKING CHANGE move to consume upstream helm charts (#14681)

**Description**

To ensure stability, we've decided to directly use upstream helm-charts
from their respective projects for operators specifically.
Mostly because they heavily rely on rbac, crds and crs, which could
cause conflicts between shipped rbac/crd and container versions.

also patches the ci for a few other operators to exclude them from
signing requirements

⚒️ Fixes  # <!--(issue)-->

**⚙️ Type of change**

- [ ] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [x] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [x] 🔃 Refactor of current code

**🧪 How Has This Been Tested?**
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Please describe the tests that you ran to verify your changes. Provide
instructions so we can reproduce. Please also list any relevant details
for your test configuration
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**📃 Notes:**
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**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [ ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [x] 🪞 I have opened a PR on
[truecharts/containers](https://github.com/truecharts/containers) adding
the container to TrueCharts mirror repo.
- [x] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

_Please don't blindly check all the boxes. Read them and only check
those that apply.
Those checkboxes are there for the reviewer to see what is this all
about and
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.github/scripts/fetch_helm_deps.sh

@@ -113,6 +113,15 @@ for idx in $(eval echo "{0..$length}"); do
               elif [[ "$name" =~ "velero" ]]; then
                   helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
                   helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "metallb" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "cloudnative-pg" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "kube-prometheus-stack" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
               elif [[ "$name" =~ "cert-manager" ]]; then
                   helm dependency build "$charts_path/$train_chart/Chart.yaml" --verify --keyring $gpg_dir/certman.gpg || \
                   helm dependency update "$charts_path/$train_chart/Chart.yaml" --verify --keyring $gpg_dir/certman.gpg || exit 1
@@ -129,6 +138,12 @@ for idx in $(eval echo "{0..$length}"); do
                   helm verify $cache_path/$repo_dir/$name-$version.tgz --keyring $gpg_dir/certman.gpg || exit 1
                 elif [[ "$name" =~ "velero" ]]; then
                    echo "Velero is not signed..."
+                elif [[ "$name" =~ "metallb" ]]; then
+                   echo "metallb is not signed..."
+                elif [[ "$name" =~ "cloudnative-pg" ]]; then
+                   echo "cloudnative-pg is not signed..."
+                elif [[ "$name" =~ "kube-prometheus-stack" ]]; then
+                   echo "kube-prometheus-stack is not signed..."
                 elif [[ ! "$train_chart" =~ incubator\/.* ]]; then
                   echo "Validating dependency signature..."
                   helm verify $cache_path/$repo_dir/$name-$version.tgz --keyring $gpg_dir/pubring.gpg || \
@@ -145,6 +160,15 @@ for idx in $(eval echo "{0..$length}"); do
               elif [[ "$name" =~ "velero" ]]; then
                   helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
                   helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "metallb" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "cloudnative-pg" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
+              elif [[ "$name" =~ "kube-prometheus-stack" ]]; then
+                  helm dependency build "$charts_path/$train_chart/Chart.yaml" || \
+                  helm dependency update "$charts_path/$train_chart/Chart.yaml"|| exit 1
               elif [[ "$name" =~ "cert-manager" ]]; then
                   helm dependency build "$charts_path/$train_chart/Chart.yaml" --verify --keyring $gpg_dir/certman.gpg || \
                   helm dependency update "$charts_path/$train_chart/Chart.yaml" --verify --keyring $gpg_dir/certman.gpg || exit 1