GH-50595: [C++]Add VisitIntegerType helper

[VedantRalekar]

This PR introduces VisitIntegerType in arrow/util/visit_type_inline.h, providing a convenient way to dispatch integer-only Arrow types using the existing visitor pattern.

Changes :

• Added VisitIntegerType based on ARROW_GENERATE_FOR_ALL_INTEGER_TYPES.
• Reused the existing VisitType dispatch pattern for consistency.
• Added support for all Arrow integer types (Int8/UInt8 through Int64/UInt64).
• Added a failure path for non-integer inputs since the helper assumes an integer type.

This will allow code such as dictionary index handling to be simplified by replacing manual integer type switches with a reusable visitor helper.

• GitHub Issue: [C++] Add a VisitIntegerType helper #50595
• GitHub Issue: ARROW-6258: [R] Add macOS build scripts #5095

[github-actions]

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See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #5095 has been automatically assigned in GitHub to PR creator.

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[github-actions]

⚠️ GitHub issue #5095 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #5095 has no components, please add labels for components.

[github-actions]

⚠️ GitHub issue #5095 has been automatically assigned in GitHub to PR creator.

[github-actions]

⚠️ GitHub issue #5095 has no components, please add labels for components.