[TK-1425] Parallelize acc tests & use gke-gcloud-auth-plugin

[alexsomesan]

Description

Acceptance tests

• [ ] Have you added an acceptance test for the functionality being added?
• [ ] Have you run the acceptance tests on this branch?

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccXXX'

...

Release Note

Release note for CHANGELOG:

...

References

Community Note

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