feat: add per-tenant time sharding for long out-of-order ingestion

[na--]

What this PR does / why we need it:

This adds support for automatically splitting incoming log streams in the distributor by injecting a __time_shard__ label. The value of that label is bounded by the ingester.max_chunk_age/2 value, which should allow the ingesters to accept all logs without rejecting them as too far behind here: https://github.com/grafana/loki/blob/c0856bf4a66fd589137576b87a80f5531992660f/pkg/ingester/stream.go#L424-L428

Special notes for your reviewer:

Checklist

• [x] Reviewed the CONTRIBUTING.md guide (required)
• [x] Documentation added
• [x] Tests updated
• [x] 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.