[prometheus-yet-another-cloudwatch-exporter] Add Gateway API HTTPRoute support

[somaz94]

Add Gateway API HTTPRoute support to the prometheus-yet-another-cloudwatch-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]

Gentle ping @cristiangreco @tristanburgess @thomaspeitz @andriikushch — this has been open since Jun 24 without a review yet.

Everything the repo asks for is in place: Chart Testing, the Integration Tests against ci/httproute-values.yaml, Super Linter, Check Generated Files and Check Title all pass, DCO is signed, and the chart version is bumped (0.47.0 → 0.48.0, still ahead of main).

The change is opt-in and off by default — with httpRoute.enabled: false the rendered output is identical to today's, so it carries no risk for existing users. Happy to rebase onto main if that helps; the branch is a bit behind but merges cleanly.