GH-964: Fix IndexOutOfBoundsException in Array.getResultSet() for JDBC clients

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What's Changed

• Fixed JDBC specification in ArrowFlightJdbcArray.getResultSet() that caused IndexOutOfBoundsException in JDBC clients like DBeaver when reading array columns
• The method returned a single-column ResultSet containing only array values, but JDBC spec requires a 2-column format
• Not it returns two columns:
  • Column 1 (INDEX): 1-based element indices per JDBC specification
  • Column 2: The actual array element values

Closes #964.

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Could this be considered a breaking-change even though it is a fix to comply with the JDBC spec? How should this be handled?

[lidavidm]

I think it's not a breaking change to make it comply with the spec.

Can we make the title descriptive of the changes?

[jbonofre]

If it could be seen as a breaking change from a code perspective, I don't think it's a breaking change as it's aligned with the spec (I would rather consider as a bug fix).