resource/helm_release: don't skip the uninstall when the release lookup fails

resourceReleaseExists reports false both when a release is genuinely absent
and when the lookup against the cluster failed, telling the two apart only
through the returned diagnostics. Delete acts on the boolean before appending
those diagnostics, so a failed lookup is indistinguishable from "already
uninstalled": the function returns early, the resource is removed from state,
and the uninstall never runs. The release stays behind in the cluster with
nothing tracking it.

We ran into the underlying error during a short API server outage on AKS,
where the same hiccup surfaced in the kubernetes provider as
"net/http: TLS handshake timeout".

Check the diagnostics first, which is what Create already does.

The identical ordering issue in Read is being fixed in #1734, so it is left
alone here.

Author: bitte-ein-bit

.changelog/1867.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+`resource/helm_release`: Fix `Delete` skipping the uninstall and dropping the resource from state when the release lookup fails because of a transient error (for example `net/http: TLS handshake timeout`), leaving the release behind in the cluster.
+```

helm/resource_helm_release.go

@@ -1251,14 +1251,20 @@ func (r *HelmRelease) Delete(ctx context.Context, req resource.DeleteRequest, re
 	name := state.Name.ValueString()
 	namespace := state.Namespace.ValueString()
 
+	// resourceReleaseExists reports false both when the release is gone and
+	// when the lookup itself failed, so the diagnostics have to be checked
+	// before treating the release as already uninstalled. Otherwise a
+	// transient error talking to the cluster ends the delete right here: the
+	// resource is dropped from state without the uninstall ever running, and
+	// the release stays behind in the cluster.
 	exists, diags := resourceReleaseExists(ctx, name, namespace, meta)
-	if !exists {
-		return
-	}
 	resp.Diagnostics.Append(diags...)
 	if resp.Diagnostics.HasError() {
 		return
 	}
+	if !exists {
+		return
+	}
 
 	// Get Helm configuration
 	actionConfig, err := meta.GetHelmConfiguration(ctx, namespace)