Validate Alloy remote writes through Cortex Tenant

General MR

Summary

• Allow ingress from alloy-metrics to the Cortex Tenant remote-write endpoint.
• Extend package CI to deploy Alloy and kube-state-metrics with Prometheus disabled, then query Mimir for an Alloy-scraped kube_pod_info metric in the configured tenant.
• Explicitly enable Alloy egress and Mimir distributor ingress in the package CI overlay to exercise the opt-in rules.
• Bump the wrapper chart to 0.8.1-bb.2, update the changelog, and regenerate the README.

Relevant logs/screenshots

• helm lint ./chart, standalone Helm renders, the combined Big Bang overlay render, and bash -n chart/tests/scripts/remote-write.sh passed.
• The prior clean-install job passed with the kube_pod_info assertion; the new CI run validates the explicit policy overrides.

Umbrella Branch

alloy-cortex-tenant-prewiring

Linked Issue

big-bang/bigbang#3464 (closed)

Upgrade Notices

N/A