loki fix(helm): Fix rendering of dnsConfig for backend, read, write, single-binary and table-manager

What this PR does / why we need it:

Fixes below templating error when specifying dnsConfig in SimpleScalable deployment mode.

Error: loki/charts/loki/templates/write/statefulset-write.yaml:151:16
  executing "loki/charts/loki/templates/write/statefulset-write.yaml" at <.>:
    wrong type for value; expected string; got map[string]interface {}

The dnsConfig property is an object so we need to use toYaml. This aligns with how it's correctly handled and working in other components.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Supersedes stale PR #15537

Checklist

[X] Reviewed the CONTRIBUTING.md guide (required)
[X] Documentation added
[ ] Tests updated
[X] Title matches the required conventional commits format, see here
- Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
[X] Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
[ ] If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR