Run Bazel test suite on Linux ARM64 platform

Refactor `UiEventHandler` tests into subclasses for stdout only, stderr only, and both.

Failed in 1m 2s
:ubuntu: Ubuntu 20.04 LTS ARM64curl -sS https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/buildkite/bazelci.py?1739561307 -o bazelci.py && python3.8 bazelci.py runner --task=ubuntu2004_arm64 --http_config=https://raw.githubusercontent.com/bazelbuild/continuous-integration/master/pipelines/bazel-linux-arm64.yml?1739561307
Waited 6s
·
Ran in 19s
Total Job Run Time: 56s