chore(chart): use example-registry placeholder in tests and CI

[aslafy-z]

What

Normalizes the placeholder image values used in tests and CI to the example-* family:

• registry/example-image becomes example-registry/example-image in application/tests/cronjob_test.yaml, deployment_test.yaml, job_test.yaml (suite fixtures and per-test values/asserts), application/ci/values.yaml, and the --set deployment.image.repository=... install flag in .github/workflows/ci.yaml
• Secondary images use a fully distinct another-example-* family: the image templating tests (uses image templating cases in the three suites) use another-example-registry/another-example-image / another-example-tag / another-example-digest instead of custom-image / custom-tag / custom-digest, and the initContainers tests in the CronJob and Job suites use another-example-registry/another-example-image:another-example-tag instead of the bare example-image:example-tag
• application/tests/__snapshot__/common_test.yaml.snap: regenerated with helm-unittest -u
• renovate.json: ignoreDeps updated to cover the example-registry / another-example-registry and example-image / another-example-image combinations

Why

registry/ reads like a real path segment. Prefixing it with example- makes every component of the placeholder reference (example-registry/example-image:example-tag) self-describing as arbitrary. The templating tests need values distinct from the suite fixture so the asserts prove the value flowed through {{ .Values.custom.image.* }} rather than the default; the another-example-* family makes that distinction obvious at a glance while staying in the same example-style vocabulary, instead of the unrelated custom-* naming. It also gives future tests that need a second placeholder container (e.g. the sidecar tests in #593) an established convention.

Notes

• No template or default values change; this only touches test inputs, CI placeholder values, and the renovate ignore list.
• openshift/oauth-proxy:latest in the deployment tests is the chart's actual default, not a placeholder, and is intentionally left as is.

Validation

• helm-unittest application: 382 tests, 37 snapshots, all passing
• ct lint: passing