feat(ingester): Change partition ingester startup sequence

[paul1r]

What this PR does / why we need it:
Partition ingesters currently stay in a "not ready" state in terms of Kubernetes health when starting until they have caught up in reading all of their data from Kafka.

This PR decouples the k8s health from the partition readiness, in that the pod should be marked as "healthy", but the partition ingester will not join the ring until the consumption lag has been processed. As the ingester joins the ring, it will briefly be marked as "not ready" while tokens are distributed to the ingester, and becomes ready very quickly after that.

Care was taken to ensure the lifecycle of classic ingesters is not impacted, as well.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[paul1r]

This is just test code that won't be in the final PR, but simulates a case where the partition ingester is delayed because of consumption lag