Automatic merge from submit-queue (batch tested with PRs 41756, 36344, 34259, 40843, 41526)
Migrate rackspace/gophercloud -> gophercloud/gophercloud
`gophercloud` is the go library we use to interact with openstack. It has recently been renamed and incorporated a number of breaking code cleanups. This change migrates the Kubernetes openstack code (openstack provider, keystone auth, cinder volumes) to the new library.
Fixes #30404
```release-note
The openstack cloud provider config no longer supports the deprecated `api-key` option.
```
Note this PR doesn't change the rackspace provider. It uses some rackspace-specific APIs and continues to use the older rackspace/gophercloud library.
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