ORC tz split 1/6: JNI plumbing and OrcTimezoneContext skeleton

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Part of the split of #4432 into smaller reviewable PRs (≤500 lines each).
Companion: NVIDIA/cudf-spark#14544

This PR brings in only the JNI surface and Java entrypoint changes:

• src/main/cpp/src/GpuTimeZoneDBJni.cpp: new JNI methods for building/releasing per-table ORC timezone context and the parse_dst_rule helper.
• src/main/cpp/src/timezones.hpp: declarations for the new convert_orc_timezones path, OrcTimezoneInfo struct, and DST rule fields.
• src/main/java/com/nvidia/spark/rapids/jni/GpuTimeZoneDB.java: OrcTimezoneContext class, convertOrcTimezones taking ColumnView, and wiring through the new native methods.
• src/main/resources/orc_timezone_info.data: delete the pre-built data file (subsequent PRs replace it with runtime-generated metadata).

The Java code references OrcTimezoneInfo.get(...) and DstRule which are introduced in #orc-tz-2 (next PR in the chain), so this intermediate branch does not compile on its own and is for review only.

Stack

1. this PR → main
2. orc-tz-2-orctzinfo-dst-extract → this branch
3. orc-tz-3-orctzinfo-runtime-build → orc-tz-2
4. orc-tz-4-cuda-civil-calendar → orc-tz-3
5. orc-tz-5-cuda-dst-gpu → orc-tz-4
6. orc-tz-6-tests → orc-tz-5 (tree identical to Support DST timezones conversion for ORC #4432)

Signed-off-by: Chong Gao chongg@nvidia.com

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NOTE: release/26.06 has been created from main. Please retarget your PR to release/26.06 if it should be included in the release.

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