Automatic merge from submit-queue (batch tested with PRs 50418, 49830, 49206, 49061, 49912)

add LocalZone into gce.conf and refactor gce cloud provider configura…

The main goal of this PR is to make gce cloud provider able to run locally. 

1. added a LocalZone parameter into gce.conf. 
2. refactor `newGCECloud` to avoid contacting metadata server if configuration is already available. 

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