After the removal of the dynamic kubelet configuration feature it became
possible to initialize logging directly after configuration parsing. The
advantage is that logs emitted by
kubeletconfigvalidation.ValidateKubeletConfiguration and
`klog.InfoS("unsupported configuration ...` already use the intended log
output.

After the code was originally added, Run was replaced by RunE. Taking advantage
of that and returning an error is cleaner.

StartFlushDaemon can be called more than once. We can take advantage of that an
eliminate the tracking of where we need to start it.

Making the LoggingConfiguration part of the versioned component-base/config API
had the theoretic advantage that components could have offered different
configuration APIs with experimental features limited to alpha versions (for
example, sanitization offered only in a v1alpha1.KubeletConfiguration). Some
components could have decided to only use stable logging options.

In practice, this wasn't done. Furthermore, we don't want different components
to make different choices regarding which logging features they offer to
users. It should always be the same everywhere, for the sake of consistency.

This can be achieved with a saner Go API by dropping the distinction between
internal and external LoggingConfiguration types. Different stability levels of
indidividual fields have to be covered by documentation (done) and potentially
feature gates (not currently done).

Advantages:

- everything related to logging is under component-base/logs;
  previously this was scattered across different packages and
  different files under "logs" (why some code was in logs/config.go
  vs. logs/options.go vs. logs/logs.go always confused me again
  and again when coming back to the code):

  - long-term config and command line API are clearly separated
    into the "api" package underneath that

  - logs/logs.go itself only deals with legacy global flags and
    logging configuration

- removal of separate Go APIs like logs.BindLoggingFlags and
  logs.Options

- LogRegistry becomes an implementation detail, with less code
  and less exported functionality (only registration needs to
  be exported, querying is internal)

It is useful to have the ability to control whether alpha or beta features are
enabled. We can group features under LoggingAlphaOptions and LoggingBetaOptions
because the configuration is designed so that each feature individually must be
enabled via its own option.

Currently, the JSON format itself is beta (graduated in 1.23) but additional
options for it were only added in 1.23 and thus are still alpha:

  $ go run ./staging/src/k8s.io/component-base/logs/example/cmd/logger.go --logging-format=json --log-json-split-stream --log-json-info-buffer-size 1M --feature-gates LoggingBetaOptions=false
  [format: Forbidden: Log format json is BETA and disabled, see LoggingBetaOptions feature, options.json.splitStream: Forbidden: Feature LoggingAlphaOptions is disabled, options.json.infoBufferSize: Forbidden: Feature LoggingAlphaOptions is disabled]

  $ go run ./staging/src/k8s.io/component-base/logs/example/cmd/logger.go --logging-format=json --log-json-split-stream --log-json-info-buffer-size 1M
  [options.json.splitStream: Forbidden: Feature LoggingAlphaOptions is disabled, options.json.infoBufferSize: Forbidden: Feature LoggingAlphaOptions is disabled]

This is the same approach that was taken for CPUManagerPolicyAlphaOptions and
CPUManagerPolicyBetaOptions.

In order to test this without modifying the global feature gate in a test file,
ValidateKubeletConfiguration must take a feature gate as argument.

API types are only supposed to have methods related to serialization.