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ARROW-10927: [Rust][Parquet] Add Decimal to ArrayBuilderReader

This PR introduces capabilities to construct a `DecimalArray` from Parquet files.

This is done by adding a new `Converter<Vec<Option<ByteArray>>, DecimalArray>` in `parquet::arrow::converter`:

```
pub struct DecimalArrayConverter {
    precision: i32,
    scale: i32,
}
```

It is then used in `ArrayBuilderReader` using a match guard to differentiate it from regular fixed size binaries:

```
  PhysicalType::FIXED_LEN_BYTE_ARRAY if cur_type.get_basic_info().logical_type() == LogicalType::DECIMAL =>
```

A test was added that uses a parquet file from `PARQUET_TEST_DATA` to check whether loading and casting to `DecimalArray` works. I did not find a corresponding json file with the correct values, but I used `pyarrow` to extract the correct values and hard coded them in the test.

I thought that this PR would require #8784 to be merged, but they are independent. I used the same JIRA issue here - I hope that this is okay.

Closes #8880 from sweb/rust-parquet-decimal-arrow-reader

Authored-by: Florian Müller <florian@tomueller.de>
Signed-off-by: Andy Grove <andygrove73@gmail.com>