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GH-38503: [Go][Parquet] Style improvement for using ArrowColumnWriter (#38581)



### Rationale for this change

Currently, `ArrowColumnWriter` seems not having bug. But the usage is confusing. For nested type,  `ArrowColumnWriter` should considering the logic below:

```
  /// 0 foo.bar
  ///       foo.bar.baz           0
  ///       foo.bar.baz2          1
  ///   foo.qux                   2
  /// 1 foo2                      3
  /// 2 foo3                      4
```

The left column is the column in root of `arrow::Schema`, the parquet itself only stores Leaf node,
so, the column id for parquet is list at right.

In the `ArrowColumnWriter`, the final argument is the LeafIdx in parquet, so, writer should considering
using `leafIdx`. Also, it need a `LeafCount` API for getting the leaf-count here.

### What changes are included in this PR?

Style enhancement for `LeafCount`, `leafIdx` and usage for `ArrowColumnWriter`

### Are these changes tested?

no

### Are there any user-facing changes?

no

* Closes: #38503

Authored-by: mwish <maplewish117@gmail.com>
Signed-off-by: Matt Topol <zotthewizard@gmail.com>