Various libraries, including stdlib, accept *log.Logger to support
optional logging. Let's expose logBridge to facilitate working with
these libraries.

stdlib examples:
* [http.Server.ErrorLog]
* [httputil.ReverseProxy.ErrorLog]

[http.Server.ErrorLog]: https://cs.opensource.google/go/go/+/refs/tags/go1.20.1:src/net/http/server.go;l=2679-2683;drc=ea4631cc0cf301c824bd665a7980c13289ab5c9d
[httputil.ReverseProxy.ErrorLog]: https://cs.opensource.google/go/go/+/refs/tags/go1.20.1:src/net/http/httputil/reverseproxy.go;l=173-176;drc=458241f981e0a8e1d9e0b2f6ae53be62f00001d2

expose logBridge via NewStandardLog()

The wrapper function solves two problems:
- Types which inherit a String implementation from some embedded type
  and then don't overwrite it log just the embedded type as string.
  Example: KubeletConfig.
- Types which have a generated String implementation and no MarshalLog
  get always logged as string, also in JSON. Example: all of the
  Kubernetes API types.

Ideally, types should get fixed to handle both cases. klog.Format is the
fallback for cases where that is not possible or not desirable: it implements
String as an indented JSON dump and MarshalLog as value dump through
reflection.

add Format wrapper

Those are types for which the Sprintf("%+v") catchall code is used.

The output of Sprintf("%+v") is neither readable nor parseable. JSON encoding
is better in both regards.

There are some downsides:
- Unexported fields don't get encoded anymore. However, the same happens
  with other backends (in particular, zapr), so one could also
  argue that making the text format behave like those others
  is good because developers notice early that they custom
  String and MarshalLog methods if they want to log such fields.
- The result KObjs (a slice) now gets encoded as array of structs.
  KObjs already got deprecated a year ago. KObjSlice should be used
  instead.

JSON as fallback encoding