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GH-41112: [C++] Clean up unused parameter warnings (#41111)

Noticed these when compiling the nanoarrow test suite with -Wextra
* GitHub Issue: #41112

### Rationale for this change

Helps clean up build warnings when compiling with -Wextra

### What changes are included in this PR?

Used Arrow macros to mark some parameters as unused

### Are these changes tested?

N/A - just ensured program compiles cleanly

### Are there any user-facing changes?

No

Authored-by: Will Ayd <william.ayd@icloud.com>
Signed-off-by: Felipe Oliveira Carvalho <felipekde@gmail.com>