apimachinery runtime: support contextual logging

In contrast to the original HandleError and HandleCrash, the new
HandleErrorWithContext and HandleCrashWithContext functions properly do contextual
logging, so if a problem occurs while e.g. dealing with a certain request and
WithValues was used for that request, then the error log entry will also
contain information about it.

The output changes from unstructured to structured, which might be a breaking
change for users who grep for panics. Care was taken to format panics
as similar as possible to the original output.

For errors, a message string gets added. There was none before, which made it
impossible to find all error output coming from HandleError.

Keeping HandleError and HandleCrash around without deprecating while changing
the signature of callbacks is a compromise between not breaking existing code
and not adding too many special cases that need to be supported. There is some
code which uses PanicHandlers or ErrorHandlers, but less than code that uses
the Handle* calls.

In Kubernetes, we want to replace the calls. logcheck warns about them in code
which is supposed to be contextual. The steps towards that are:
- add TODO remarks as reminder (this commit)
- locally remove " TODO(pohly): " to enable the check with `//logcheck:context`,
  merge fixes for linter warnings
- once there are none, remove the TODO to enable the check permanently

hack/logcheck.conf

@@ -24,6 +24,7 @@ structured k8s.io/apiserver/pkg/server/options/encryptionconfig/.*
 # The following packages have been migrated to contextual logging.
 # Packages matched here do not have to be listed above because
 # "contextual" implies "structured".
+contextual k8s.io/apimachinery/pkg/util/runtime/.*
 contextual k8s.io/client-go/metadata/.*
 contextual k8s.io/client-go/tools/events/.*
 contextual k8s.io/client-go/tools/record/.*