[VL][Delta] Add native Delta DV reader support

[malinjawi]

What changes are proposed in this pull request?

This PR is the second step in the split Delta deletion-vector (DV) stack, following #12001.

It adds the native Velox-side Delta DV reader layer that consumes the roaring bitmap payload facilities introduced by #12001, without adding the JVM-side Delta scan metadata handoff yet.

Main changes:

• add a native Delta connector and data source backed by the Hive connector/data source infrastructure
• register a scoped Delta connector alongside the existing scoped Hive connector for each Velox runtime
• add Delta split metadata types for:
  • deletion-vector descriptors
  • protocol metadata
  • file statistics used for DV validation
  • serialized split payload buffer views
• add DeltaDeletionVectorReader to load materialized Delta DV payloads using RoaringBitmapArray
• add DeltaSplitReader to validate DV protocol/statistics metadata and apply row-index filtering semantics
• add focused native unit coverage for connector setup, split metadata, and deletion-vector reader behavior

This PR is intentionally native-reader only:

• no JVM-side Delta scan metadata handoff yet
• no end-to-end Delta scan offload behavior change yet

Those pieces will be added in follow-up split PRs.

issue #11901.

How was this patch tested?

Added focused native test coverage in:

• cpp/velox/compute/delta/tests/DeltaConnectorTest.cpp
• cpp/velox/compute/delta/tests/DeltaSplitTest.cpp
• cpp/velox/compute/delta/tests/DeltaDeletionVectorReaderTest.cpp

Covered cases:

• Delta connector configuration and connector properties
• split-carried deletion-vector descriptors and logical row-count accounting
• loading materialized DV payloads from RoaringBitmapArray
• row deletion checks and keep/drop filter decisions
• empty payload handling and invalid payload rejection
• protocol/statistics validation for DV-bearing splits

Validation run:

• fork preview CI against malinjawi/incubator-gluten:main on the combined PR2 branch: all checks passed after rerunning two infra-flaky jobs
• local git diff --check upstream/main...HEAD
• local clang-format pass with /opt/homebrew/opt/llvm@15/bin/clang-format over changed C++ files

Was this patch authored or co-authored using generative AI tooling?

Generated-by: IBM BOB

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