BDX-645: prototype PollInfo support for JDBC

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Summary

BDX-645 POC for progressive PollFlightInfo consumption in Arrow Java JDBC without changing the JDBC API.

• Returns the existing ResultSet when the first endpoint is published.
• Polls the next continuation only when ResultSet.next() exhausts current endpoints.
• Validates the cumulative endpoint prefix and queues only appended endpoints.
• Surfaces a late continuation failure at the next ResultSet.next() boundary; no fallback or re-execution.
• Preserves initial-UNIMPLEMENTED fallback/cache, connection opt-out, one operation deadline, and best-effort cancellation on cancel or incomplete close.

Progressive request flow

sequenceDiagram
    participant App as JDBC application
    participant Driver as JDBC driver
    participant Server as Flight SQL server
    App->>Driver: executeQuery
    Driver->>Server: PollFlightInfo original
    Server-->>Driver: Endpoint 1 and continuation
    Driver-->>App: Existing ResultSet
    App->>Driver: next
    Driver->>Server: DoGet endpoint 1
    Server-->>Driver: Row 1
    Driver-->>App: Row 1
    App->>Driver: next
    Driver->>Server: PollFlightInfo continuation
    Server-->>Driver: Endpoint 1 plus endpoint 2
    Driver->>Server: DoGet endpoint 2
    Server-->>Driver: Row 2
    Driver-->>App: Row 2

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Validation

• Focused PollInfo: 12/12 pass.
• Shared progressive suite: 11/11 pass.
• Combined final run: 23/23 pass, Checkstyle clean.
• T2 server trace: Poll, DoGet, Poll, DoGet, Poll, DoGet.
• Mermaid rendered successfully with Mermaid CLI 11.17.0.

Feasibility: yes, with documented Java helper/API-boundary limitations.

Jira: BDX-645
Fixture: dremio-employees/helder.gregorio#7