[GeorgiaPreda]

Rationale for this change

Fixes #54688. A Ruby buffer’s input can be garbage-collected while an array still references its native storage, causing subsequent reads to return corrupted values.

What changes are included in this PR?

• Copy String and GLib::Bytes inputs into native-owned Arrow buffer storage.
• Remove the redundant Ruby constructor-argument GC guard for Buffer.
• Add regression tests covering garbage collection with chunked arrays and slices, and mutation of the original String.

Are these changes tested?

The corruption was reproduced before the fix. After the fix:

• 1,800 selected Ruby tests passed.
• 36 GLib buffer and stream tests passed.
• RuboCop, Ruby syntax checks, and git diff --check passed.

Are there any user-facing changes?

Buffer contents remain valid when arrays outlive their Ruby wrappers. Constructing a buffer from a String or GLib::Bytes now copies the data into native-owned storage. Subsequent mutations to the original String no longer change the buffer’s contents.

This PR contains a "Critical Fix". It prevents corrupted array values caused by accessing input storage after Ruby garbage collection.

Was AI used for this PR?

PR code and description written by:

• Human
• AI

Reviewed before submission by:

• Human
• AI
• Not reviewed

• GitHub Issue: [Ruby] Memory passed to Arrow::Buffer.new is freed by GC while an array still refers to it #54688

[github-actions]

⚠️ GitHub issue #54688 has been automatically assigned in GitHub to PR creator.