Automatic merge from submit-queue
Fix kube-apiserver crash when patching TPR data
**What this PR does / why we need it**: While trying to do a strategic merge patch, kube-apiserver crashes with a nil pointer dereference because `UnsafeConvertor` is `nil` for TPR data resources here: https://github.com/kubernetes/kubernetes/blob/master/pkg/master/thirdparty/thirdparty.go#L314-L337.
This PR does not make strategic merge patch work on TPR data but makes sure that the kube-api server does not crash while trying to do so.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#44587
**Special notes for your reviewer**:
**Release note**:
```
NONE
```
While trying to do a strategic merge patch,
kube-apiserver crashes with a nil pointer dereference because
UnsafeConvertor is nil for TPR data resources.
Fixes#44587
Automatic merge from submit-queue (batch tested with PRs 39648, 38167, 39591, 39415, 39612)
Add verbs to thirdparty resources in discovery
The namespace controller ignores thirdparty resources right now because verbs are not set. This PR sets a static list of verbs.
Moreover, integration tests are added for the discovery info of thirdparty resources.
/cc @zhouhaibing089
- move rest handler into handlers package
- move errors into handlers/errors package
- move negotation code into handlers/negotation package
- move http response writer helpers into handlers/responsewriter package
- split up pkg/apiserver/apiserver.go
Note: this is only an intermediate step towards a proper genericapiserver
package hierarchy.
