[Python][Parquet] Support wiriting decimals as integers

[zmanji]

Describe the enhancement requested

#15244 updated the parquet writer to store decimals as integers. This is not yet exposed to the Python bindings.

Component(s)

Parquet, Python

[mapleFU]

cc @wgtmac

Do we have a way to represent decimal using int32/int64 in arrow?

[wgtmac]

cc @wgtmac

Do we have a way to represent decimal using int32/int64 in arrow?

I don't think so.