fix(ingress-controller): align listener port matching default

[kayx23]

Summary

• change the APISIX Ingress Controller chart default from listenerPortMatchMode: auto to off, matching the controller 2.2.0 safety default
• change the ConfigMap fallback to off and bump the chart to 1.3.1
• document the upgrade impact and how to retain auto or explicit
• add a rendered-config regression test for both the default and an explicit auto override
• regenerate the chart README and run the regression test in CI

Why

APISIX Ingress Controller changed its omitted-field default to off in apache/apisix-ingress-controller#2804 after review reproduced a common mismatch: a Gateway listener declares port 80, Kubernetes maps Service port 80 to APISIX port 9080, and an injected server_port == 80 predicate causes the route to miss.

Chart 1.3.0 still explicitly renders auto, so Helm users never receive the controller's safer fallback. This PR aligns the dedicated chart with the released controller contract.

Users who intentionally rely on listener-port matching can preserve the old chart behavior with:

config:
  listenerPortMatchMode: auto

The APISIX umbrella chart still pins controller chart 1.3.0. Its dependency should be updated after 1.3.1 is published; it cannot safely reference the unpublished remote chart in this PR.

Validation

• bash -n test/ingress-controller-config-defaults.sh
• bash test/ingress-controller-config-defaults.sh
• default, auto, and explicit helm template renders
• helm package charts/apisix-ingress-controller
• helm-docs@v1.11.0 regeneration is idempotent
• upstream CI chart-testing image:

  ct lint --validate-maintainers=false \
    --charts charts/apisix-ingress-controller

  Result: 1 chart linted, 0 failed
• workflow YAML parse and git diff --check

Closes #1001.

Related: api7/api7-ingress-controller#462, #997.