GH-49288: [C++][ORC] Add OrcFileFragment with stripe-level subsetting

[ShreyeshArangath]

Rationale for this change

The ORC dataset integration currently lacks stripe-level subsetting support. When scanning ORC files through the Dataset API, there is no way to select specific stripes. The entire file is always read. This is a gap compared to ParquetFileFragment, which provides row-group-level subsetting via Subset(), row_groups(), and MakeFragment(..., row_groups).

What changes are included in this PR?

Modeled after the ParquetFileFragment design, we introduce stripe-aware ORC fragments so callers can target specific stripes during planning and scanning (instead of always reading the full file). This adds a small, consistent surface area in both C++ (and Python, separate issue):

An ORC-specific fragment type that can represent either the full file, or a subset of the file defined by stripe IDs
Fragment subsetting via a subset(...)/Subset(...) API, analogous to Parquet row-group subsetting.
Scan behavior that honors stripe selection, so execution reads only the requested stripes.
Correct row counting for subset fragments, where row counts reflect only the selected stripes

Are these changes tested?

• Unit tested

Are there any user-facing changes?

The C++ API has the following changes

• OrcFileFragment class with stripe_ids() and Subset() methods
• OrcFileFormat::MakeFragment(source, partition_expression, physical_schema, stripe_ids) overload

Though, there are no breaking changes. Existing ORC scanning behavior is unchanged when no stripe IDs are specified.

• AI Usage disclosure: I did use an AI IDE to make this PR but I reviewed the code and stand behind its changes and tests.

• GitHub Issue: [C++][ORC] Add OrcFileFragment with stripe-level subsetting #49288

[github-actions]

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See also:

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• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #49288 has been automatically assigned in GitHub to PR creator.