[FLINK-38857][model] Add sequence ID auto-increment support for Triton inference

[featzhang]

What is the purpose of the change

This PR FLINK-38857 adds sequence ID auto-increment strategy support for Triton Inference Server integration in Flink, addressing the need for sequence isolation across job failovers and restarts.

Brief change log

• Add sequence-id-auto-increment configuration option in TritonOptions
• Implement auto-increment logic in TritonInferenceModelFunction
  • Generate unique sequence IDs: {sequence-id}-{subtask-index}-{counter}
  • Initialize AtomicLong counter in open() method
  • Increment counter for each inference request
• Add validation to ensure sequence-id is configured when auto-increment is enabled
• Add detailed logging for debugging sequence ID generation

Use Case

This feature is particularly useful for non-reentrant models where:

• Duplicate inference requests must be avoided after failover
• Sequence batching requires strict isolation between parallel instances
• Models maintain stateful context that cannot handle repeated sequence IDs

Example Configuration

CREATE MODEL my_triton_model WITH (
  'provider' = 'triton',
  'endpoint' = 'https://triton-server:8000/v2/models',
  'model-name' = 'my_stateful_model',
  'sequence-id' = 'flink-job-123',
  'sequence-id-auto-increment' = 'true',  -- Enable auto-increment
  'sequence-start' = 'true',
  'sequence-end' = 'true'
);

Sequence ID Format

When auto-increment is enabled, sequence IDs follow this pattern:

{base-sequence-id}-{subtask-index}-{counter}
Example: flink-job-123-0-0, flink-job-123-0-1, flink-job-123-1-0

This ensures:

• Unique sequences across parallel subtasks (via subtask-index)
• Monotonically increasing sequences per subtask (via counter)
• Sequence isolation across job restarts (new counter starts from 0)

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

• Manual testing with Triton Inference Server
• Code formatting verified with Spotless

Does this pull request potentially affect one of the following parts

• Dependencies: no
• The public API: yes (adds new configuration option)
• The serializers: no
• The runtime per-record code paths: no
• Anything that affects deployment or recovery: JobManager, Checkpoint Coordinator, State backends, etc.: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? JavaDocs

Related Issues

Closes #FLINK-38857

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CI report:

• 2d00ec8 Azure: FAILURE

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