feat: Multi-tenancy for Parseable server

[parmesant]

This is a WIP

PR to introduce multi-tenancy to parseable server

Description

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.

Summary by CodeRabbit

• New Features

  • Multi-tenant mode: per-tenant isolation, tenant management, and tenant-scoped operations across the platform.

• Improvements

  • Tenant-aware RBAC, alerts/targets, ingestion, querying, storage, retention, hot-tier, dashboards, filters, correlations, OTEL and LLM flows.
  • Metrics, billing and observability now labeled and aggregated per tenant for accurate per-tenant reporting.

• Chores

  • CLI/runtime flag to enable multi-tenancy and tenant lifecycle utilities.