feat: historical tier aliasing support in coordinator dynamic config

[jtuglu1]

Description

Introduces historical tier aliases in the Coordinator dynamic config. This allows usage of a virtual "alias" tier in retention rules, e.g. hot to map to N other historical tiers. The alias tier is virtual (it itself doesn't store segments), but instead acts as a single identifier for a group of replica tiers. This reduces friction for operators (to not need to duplicate their retention rules N times) as well as enabling use-cases like:

1. Rolling deployments that use historical tiering for query/data isolation across versions (e.g. ensure new version of historical on hot_new and old version of historical on hot_old load the same data).
2. Historical tiers to be mirrored across different regions/AZs for fault-tolerance.

Release note

Introduces historical tier aliases in the Coordinator dynamic config. This allows usage of a virtual "alias" tier in retention rules, e.g. hot to map to N other historical tiers.

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.