fix gke provisioning form stale data

[mantis-toboggan-md]

Summary

Fixes #11864

This PR updates the gke provisioning form to ensure that any default configuration applied when creating clusters copies the defaults defined in the component instead of modifying the default configuration object, so that when the component is reused, the default configuration has not been changed.

Areas or cases that should be tested

1. Create a new GKE cluster and enable private cluster, private endpoint, and master authorized network (all under the advanced section of the networking tab)
2. After saving, go to create another GKE cluster: verify that the advanced networking section has been reset to default values (all 3 checkboxes unchecked)

Areas which could experience regressions

none

Checklist

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• The PR has been self reviewed
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• The PR has automated tests or clear instructions for manual tests and the linked issue has appropriate QA labels, or tests are not needed
• The PR has reviewed with UX and tested in light and dark mode, or there are no UX changes

[eva-vashkevich]

lgtm