Run Github Actions on GCP workers in the apache-beam-testing project

[damccorm]

Objective: migrate the runners of the GitHub CI/CD pipeline (GitHub Actions or GAs) over to the Apache Beam GCP infrastructure; GKE in this case.

Imported from Jira BEAM-12812. Original Jira may contain additional context.
Reported by: kileys.

[damccorm]

Unable to assign user @dannymartinm. If able, self-assign, otherwise tag @damccorm so that he can assign you. Because of GitHub's spam prevention system, your activity is required to enable assignment in this repo.

[damccorm]

The following subtask(s) are associated with this issue: #21107

[dannymartinm]

Hi @damccorm , could you assign me this issue please? Thanks!

[damccorm]

Sure! With #21719 merged you should be able to self assign with the command .take-issue though, so you should be able to do that going forward! Let me know if you run into any issues with that