Automatic merge from submit-queue (batch tested with PRs 38076, 38137, 36882, 37634, 37558)
Allow backendpools in Azure Load Balancers which are not owned by cloud provider
**What this PR does / why we need it**: It fixes#36880
**Which issue this PR fixes**: fixes#36880
**Special notes for your reviewer**:
**Release note**:
```release-note
Allow backendpools in Azure Load Balancers which are not owned by cloud provider
```
Instead of bailing out when we find another backend pool, we just ignore
other backend pools and add ours to the list of existing.
Fixes#36880
We had another bug where we confused the hostname with the NodeName.
To avoid this happening again, and to make the code more
self-documenting, we use types.NodeName (a typedef alias for string)
whenever we are referring to the Node.Name.
A tedious but mechanical commit therefore, to change all uses of the
node name to use types.NodeName
Also clean up some of the (many) places where the NodeName is referred
to as a hostname (not true on AWS), or an instanceID (not true on GCE),
etc.
