[Backport release-1.6] fix(tenant): skip Cilium policies on isp-hosted without Cilium - #5080

…vive uninjected values (#5141)

## What this PR does

Backport of #3647 to release-1.6.

Since #5080 (backport of #4710) `tenant.ciliumPolicies` calls
`cozy-lib.bundle-name`, and on release-1.6 that helper still does `index
.Values._cluster "bundle-name"`, which fails with `index of untyped nil`
when `_cluster` is not set. Tenant export-proxy suite
(`tests/networkpolicy_vm_exportproxy_test.yaml`) sets no `_cluster`, so
all four cases fail and unit tests are red on every PR against
release-1.6, including batch #5089. #5080 set `_cluster: {}` only in its
own suite, that's why it passed there.

#3647 guards the map in every cozyconfig helper and adds cozy-lib-tests
suite for injected and uninjected state. It applies cleanly, diff is
identical to main.

Checked locally (helm-unittest is not installed here, CI runs it):

- export-proxy suite renders fail on current branch and pass with this
change;
- new cozyconfig suite passes, its uninjected case fails against old
helpers;
- all 34 charts using cozy-lib render the same before and after with
realistic `_cluster` / `_namespace` (apart from generated passwords),
only tenant chart with nothing injected changes, it doesn't fail in
`networkpolicy.yaml` anymore.

Plain `helm template` of tenant chart without `_cluster` still fails in
`keycloakgroups.yaml`, main fixed it separately in #3636. Unit tests are
not affected, suite renders only templates it names.

### Screenshots

Not a UI change.

### Downstream repositories

- [x] No downstream repository is affected by this change
- [ ] [cozystack/website](https://github.com/cozystack/website) -
follow-up:
- [ ]
[cozystack/terraform-provider-cozystack](https://github.com/cozystack/terraform-provider-cozystack)
- follow-up:
- [ ]
[cozystack/ansible-cozystack](https://github.com/cozystack/ansible-cozystack)
- follow-up:
- [ ] [cozystack/ccp](https://github.com/cozystack/ccp) - follow-up:
- [ ] [cozystack/talm](https://github.com/cozystack/talm) - follow-up:
- [ ] [cozystack/cozyhr](https://github.com/cozystack/cozyhr) -
follow-up:
- [ ] [cozystack/cozy-proxy](https://github.com/cozystack/cozy-proxy) -
follow-up:
- [ ]
[cozystack/cozystack-telemetry-server](https://github.com/cozystack/cozystack-telemetry-server)
- follow-up:
- [ ]
[cozystack/external-apps-example](https://github.com/cozystack/external-apps-example)
- follow-up:
- [ ] [cozystack/examples](https://github.com/cozystack/examples) -
follow-up:

### Release note

```release-note
fix(cozy-lib): the cozyconfig helpers now return their documented empty defaults when the platform has not injected `_cluster` / `_namespace`, instead of aborting the render, so a chart using them can be rendered and unit-tested on its own
```