GH-47769: [C++] Sve dynamic dispatch

[AntoinePrv]

Rationale for this change

Just like we dynamically dispatch to AVX2 on x86 CPUs, we want to dynamically dispatch to more advanced SIMD extension on ARM64 chips.

What changes are included in this PR?

• A new macro to enable selecting the runtime SVE version
• Detection of the ARM64 CPU features available at runtime
• Adding SVE to the dynamic dispatch for bit unpacking algorithms.

Are these changes tested?

Are there any user-facing changes?

No.

• GitHub Issue: [C++] Add dynamic dispatch on ARM64 #47769

[github-actions]

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See also:

• Other pull requests
• Contribution Guidelines - Contributing Overview

[github-actions]

⚠️ GitHub issue #47769 has been automatically assigned in GitHub to PR creator.