GH-34561: [C++] Implement RunEndEncodedBuilder::AppendEmptyValues() - #34562

• Closes: [C++] Implement missing RunEndEncodedBuilder::AppendEmptyValues() #34561

⚠️ GitHub issue #34561 has been automatically assigned in GitHub to PR creator.

@zeroshade

The failure doesn't appear related at all to this change, so I think it's fine for now.

Benchmark runs are scheduled for baseline = 8ea3769 and contender = 3df5ba8. 3df5ba8 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
[Failed ⬇️1.0% ⬆️0.09%] test-mac-arm
[Finished ⬇️0.26% ⬆️0.0%] ursa-i9-9960x
[Finished ⬇️0.97% ⬆️0.0%] ursa-thinkcentre-m75q
Buildkite builds:
[Finished] 3df5ba8b ec2-t3-xlarge-us-east-2
[Finished] 3df5ba8b test-mac-arm
[Finished] 3df5ba8b ursa-i9-9960x
[Finished] 3df5ba8b ursa-thinkcentre-m75q
[Finished] 8ea37690 ec2-t3-xlarge-us-east-2
[Failed] 8ea37690 test-mac-arm
[Finished] 8ea37690 ursa-i9-9960x
[Finished] 8ea37690 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