Derive ArrowPrimitiveType for Decimal128Type and Decimal256Type (#2637)

[tustvold]

Which issue does this PR close?

Part of #2637

Rationale for this change

This allows creating PrimitiveArrays with decimal types, subsequent PRs will flesh out support for this, before switching over the definitions of Decimal128Array and Decimal256Array

What changes are included in this PR?

Adds the ability to declare PrimitiveArray containing decimal data

Are there any user-facing changes?

No

[viirya]

There are many CI failures which look weird, but seems unrelated.

[viirya]

May need to re-trigger CI.

[ursabot]

Benchmark runs are scheduled for baseline = c93ce39 and contender = 37c8679. 37c8679 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