[prometheus-statsd-exporter] Add Gateway API HTTPRoute support

[somaz94]

Add Gateway API HTTPRoute support to the prometheus-statsd-exporter chart, mirroring the pattern already merged for the prometheus, prometheus-pushgateway, alertmanager, prometheus-blackbox-exporter, and prometheus-json-exporter charts.

The HTTPRoute is opt-in and disabled by default, so the default render is unchanged.

Validation:

• helm template renders nothing when route.main.enabled=false (default)

• helm template renders a valid HTTPRoute with ci/httproute-values.yaml (numeric backend port, parentRefs, hostnames, filters, additionalRules)

• httpsRedirect=true renders only the RequestRedirect filter

• ct lint --config .github/linters/ct.yaml passes

• helm install --dry-run=server against a kind cluster with Gateway API CRDs validates the rendered HTTPRoute against the live CRD schema

• DCO signed

[somaz94]

Hi @scDisorder — gentle ping on this one.

It's the same opt-in Gateway API HTTPRoute pattern as the sibling PRs from the same batch that have since merged (#7024, #7028, #7029, #7031, #7032). Default is httpRoute.enabled: false with a ci/httproute-values.yaml test case, so existing users are unaffected. CI is green.

Happy to rebase or adjust anything if you'd prefer a different shape.