feat: Add privateWorkerPool and location configuration for gcb

[ericzzzzzzz]

Fixes: #7342

Description

• cherry-pick privateWorkerPool support from main
• cherry-pick region configuration in googleCouldBuild support from main
• implement change to support configure the region, if workerPool is configured, build location is still deduced from workerPool. If not and region is configured, region in the configuration will be used as build location.

User facing changes

• Add privateWorkerPool and region configuration for gcb, so users are able to configure region to run gcb

Test Plan

• change this line to MarkIntegrationTest(t, CanRunWithoutGcp) then manually run this test
• enter gcp console, select k8s-skaffold project, then check the build history from asia-east1, should be able to find the build detail.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (v1@a3e0b76). Click here to learn what that means.
The diff coverage is n/a.

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  Hits          ?    18148           
  Misses        ?     7240           
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