Add configurable truncation for string columns

[jaykanakiya]

Summary

Adds a configurable maximum string length for string dimension columns. Strings exceeding the limit are truncated during ingestion.

• Global config: druid.indexing.formats.maxStringLength
• Per-dimension override: maxStringLength field in the dimension spec

Release note

Added a new maxStringLength configuration for string dimensions that truncates values exceeding the specified length during ingestion. Can be set globally via druid.indexing.formats.maxStringLength or per-dimension in the ingestion spec.

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Key changed/added classes in this PR

• DefaultColumnFormatConfig
• StringDimensionSchema
• StringDimensionHandler
• StringDimensionIndexer

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This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added or updated version, license, or notice information in licenses.yaml
• 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.

[clintropolis]

drive by comment (i'll have a closer look at rest of PR later)

instead of adding additional arguments here, I was hoping to deprecate these arguments in favor of adding a column format spec similar to was done for auto/json columns in #17762, which could serve as a reference for how this should be wired up. I was planning to move the existing createBitmapIndex and multiValueHandling into such a spec, but just haven't got to it yet. I think this would be much cleaner and less disruptive to call sites going forward. It also allows wiring up to IndexSpec to be able to define job level defaults as a middle place between per column and system wide.

[jaykanakiya]

Thanks for taking a look @clintropolis. Adding something like StringCommonFormatColumnFormatSpec would make it cleaner and makes sense to consolidate the configs there. Since it seems like a bigger refactor, does it make sense to do it in a follow up? Let me know what you think.