Merge pull request #52855 from NickrenREN/remove-rackspace

Automatic merge from submit-queue (batch tested with PRs 52880, 52855, 52761, 52885, 52929). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>..

Remove cloud provider rackspace

**What this PR does / why we need it**:
For now, we have to implement functions in both `rackspace` and `openstack` packages if we want to add function for cinder, for example [resize for cinder](kubernetes/kubernetes#51498).  Since openstack has implemented all the functions rackspace has,  and rackspace is considered deprecated for a long time, [rackspace deprecated](rackspace/gophercloud#592) ,
after talking with @mikedanese  and @jamiehannaford offline ,  i sent this PR to remove `rackspace` in favor of `openstack`

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #52854

**Special notes for your reviewer**:

**Release note**:
```release-note
The Rackspace cloud provider has been removed after a long deprecation period. It was deprecated because it duplicates a lot of the OpenStack logic and can no longer be maintained. Please use the OpenStack cloud provider instead.
```

openstack.go

@@ -484,7 +484,6 @@ func (os *OpenStack) HasClusterID() bool {
 func (os *OpenStack) LoadBalancer() (cloudprovider.LoadBalancer, bool) {
 	glog.V(4).Info("openstack.LoadBalancer() called")
 
-	// TODO: Search for and support Rackspace loadbalancer API, and others.
 	network, err := os.NewNetworkV2()
 	if err != nil {
 		return nil, false