ARROW-17390: [Go] Add union scalar types

[zeroshade]

No description provided.

[github-actions]

https://issues.apache.org/jira/browse/ARROW-17390

[ursabot]

Benchmark runs are scheduled for baseline = e8ed4c2 and contender = a4cc441. a4cc441 is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Finished ⬇️0.0% ⬆️0.0%] ec2-t3-xlarge-us-east-2
[Finished ⬇️0.71% ⬆️0.03%] test-mac-arm
[Failed ⬇️0.55% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.21% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] a4cc441e ec2-t3-xlarge-us-east-2
[Finished] a4cc441e test-mac-arm
[Failed] a4cc441e ursa-i9-9960x
[Finished] a4cc441e ursa-thinkcentre-m75q
[Finished] e8ed4c2f ec2-t3-xlarge-us-east-2
[Finished] e8ed4c2f test-mac-arm
[Failed] e8ed4c2f ursa-i9-9960x
[Finished] e8ed4c2f ursa-thinkcentre-m75q
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

[ursabot]

['Python', 'R'] benchmarks have high level of regressions.
test-mac-arm
ursa-i9-9960x