Fix indentation issue in Cilium values file and ensure booleans are lowercase (#12280)

This patch fixes the indentation in the `encryption` section.
Previously configuration like this:

```yml
cilium_encryption_enabled: true
cilium_encryption_type: wireguard
```

Would template to a `values.yaml` file with indentation that looks like this:

```yml
encryption:
  enabled: True
    type: wireguard
    nodeEncryption: False
```

instead of this:

```yml
encryption:
  enabled: true
  type: wireguard
  nodeEncryption: false
```

This syntax issue causes an error during Cilium installation.

This patch also makes all boolean values in this template file go through the `to_json` filter.
Since values like `True` and `False` are not compliant with the YAML v1.2 spec,
avoiding them is preferable.

`to_json` may be used for all other values in this template to ensure we end up with
a valid YAML document in all cases (even when various strings include special characters),
but this was left for another (future) patch.