Enable casting between Dictionary of DecimalArray and DecimalArray

[viirya]

Which issue does this PR close?

Closes #3237.
Closes #3250.

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

[viirya]

Not add tests yet. As #3222 moves tests, I will add tests after that is merged.

EDIT: tests added.

[tustvold]

These appear to duplicate a block lower down in the match tree

        (Dictionary(index_type, _), _) => match **index_type {
            Int8 => dictionary_cast::<Int8Type>(array, to_type, cast_options),
            Int16 => dictionary_cast::<Int16Type>(array, to_type, cast_options),
            Int32 => dictionary_cast::<Int32Type>(array, to_type, cast_options),
            Int64 => dictionary_cast::<Int64Type>(array, to_type, cast_options),
            UInt8 => dictionary_cast::<UInt8Type>(array, to_type, cast_options),
            UInt16 => dictionary_cast::<UInt16Type>(array, to_type, cast_options),
            UInt32 => dictionary_cast::<UInt32Type>(array, to_type, cast_options),
            UInt64 => dictionary_cast::<UInt64Type>(array, to_type, cast_options),
            _ => Err(ArrowError::CastError(format!(
                "Casting from dictionary type {:?} to {:?} not supported",
                from_type, to_type,
            ))),
        },
        (_, Dictionary(index_type, value_type)) => match **index_type {
            Int8 => cast_to_dictionary::<Int8Type>(array, value_type, cast_options),
            Int16 => cast_to_dictionary::<Int16Type>(array, value_type, cast_options),
            Int32 => cast_to_dictionary::<Int32Type>(array, value_type, cast_options),
            Int64 => cast_to_dictionary::<Int64Type>(array, value_type, cast_options),
            UInt8 => cast_to_dictionary::<UInt8Type>(array, value_type, cast_options),
            UInt16 => cast_to_dictionary::<UInt16Type>(array, value_type, cast_options),
            UInt32 => cast_to_dictionary::<UInt32Type>(array, value_type, cast_options),
            UInt64 => cast_to_dictionary::<UInt64Type>(array, value_type, cast_options),
            _ => Err(ArrowError::CastError(format!(
                "Casting from type {:?} to dictionary type {:?} not supported",
                from_type, to_type,
            ))),
        },

Perhaps we could just move the decimal matches lower?

Edit: In fact moving the dictionary matches to the top would also simplify the list handling as well, what do you think?

[viirya]

Good catch! Moved the dictionary matches to the top.

[ursabot]

Benchmark runs are scheduled for baseline = 796b670 and contender = 09d5f02. 09d5f02 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java