arrow

GH-38432: [C++][Parquet] Try to fix performance regression in the DictByteArrayDecoderImpl (#38784)



### Rationale for this change

Do some changes mentioned in https://github.com/apache/arrow/issues/38432

I believe this might fix https://github.com/apache/arrow/issues/38577

Problem1:

The `BinaryHelper` might call `Prepare()` and `Prepare(estimated-output-binary-length)` for data. This might because:

1. For Plain Encoding ByteArray, the `len_` is similar to the data-page size, so `Reserve` is related.
2. For Dict Encoding. The Data Page is just a RLE encoding Page, it's `len_` might didn't directly related to output-binary. 

Problem2:

`Prepare` using `::arrow::kBinaryMemoryLimit` as min-value, we should use `this->chunk_space_remaining_`.

Problem3:

`std::optional<int64_t>` is hard to optimize for some compilers

### What changes are included in this PR?

Mention the behavior of BinaryHelper. And trying to fix it.

### Are these changes tested?

No

### Are there any user-facing changes?

Regression fixes

* Closes: #38432

Lead-authored-by: mwish <maplewish117@gmail.com>
Co-authored-by: mwish <1506118561@qq.com>
Co-authored-by: Gang Wu <ustcwg@gmail.com>
Signed-off-by: Antoine Pitrou <antoine@python.org>