logs: remove deprecated klog flags

[pohly]

What type of PR is this?

/kind cleanup
/kind api-change

What this PR does / why we need it:

This completes the deprecation of klog flags which are no longer supported.
klog itself continues to support them, but Kubernetes components don't. This
makes the command line interfaces simpler and reduces the attack surface
because less functionality is exposed.

Which issue(s) this PR fixes:

Fixes #kubernetes/enhancements#2845

Special notes for your reviewer:

For example, kube-controller-manager now has:

Logs flags:

  --log-flush-frequency duration
            Maximum number of seconds between log flushes (default 5s)
  --log-json-info-buffer-size quantity
            [Alpha] In JSON format with split output streams, the info messages can be buffered for a while to increase performance. The default value of zero
            bytes disables buffering. The size can be specified as number of bytes (512), multiples of 1000 (1K), multiples of 1024 (2Ki), or powers of those (3M,
            4G, 5Mi, 6Gi). Enable the LoggingAlphaOptions feature gate to use this.
  --log-json-split-stream
            [Alpha] In JSON format, write error messages to stderr and info messages to stdout. The default is to write a single stream to stdout. Enable the
            LoggingAlphaOptions feature gate to use this.
  --logging-format string
            Sets the log format. Permitted formats: "json" (gated by LoggingBetaOptions), "text".
   -v, --v Level
            number for the log level verbosity
  --vmodule pattern=N,...
            comma-separated list of pattern=N settings for file-filtered logging (only works for text log format)

Misc flags:

  --kubeconfig string
            Path to kubeconfig file with authorization and master location information.
  --master string
            The address of the Kubernetes API server (overrides any value in kubeconfig).

Global flags:

 -h, --help
            help for kube-controller-manager
  --version version[=true]
            Print version information and quit

For details see
https://github.com/kubernetes/enhancements/tree/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components

Does this PR introduce a user-facing change?

Legacy klog flags are no longer available. Only `-v` and `-vmodule` are still supported.

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

- [KEP]: https://github.com/kubernetes/enhancements/issues/2845
- [Usage]: https://github.com/kubernetes/enhancements/blob/master/keps/sig-instrumentation/2845-deprecate-klog-specific-flags-in-k8s-components/README.md#user-stories

/assign @serathius

[pohly]

@serathius: do we still want to have this line here?

Non-default formats don't honor these flags: --vmodule.

It only lists one flag, and that flag itself now says "only works for text log format".

[serathius]

/lgtm

[pohly]

/hold

I forgot to mention that kubernetes/test-infra#27305 needs to be merged first.

[pohly]

@serathius so do you want me to remove "Non-default formats don't honor these flags: --vmodule." or keep it?

[serathius]

I don't think "Non-default formats don't honor these flags: --vmodule." is needed, we can remove it.

[yuzhiquan]

Suggested change

	Copyright 202 The Kubernetes Authors.
	Copyright 2022 The Kubernetes Authors.

[pohly]

Oh, the good old times of 202! You are right of course, good catch.

[pohly]

I don't think "Non-default formats don't honor these flags: --vmodule." is needed, we can remove it.

That's also my preference. While at it, I also removed "Non-default choices are currently alpha and subject to change without warning." because that has been wrong for a while now.

We don't need that sentence because non-GA formats list the corresponding feature gate:

          --logging-format string
                    Sets the log format. Permitted formats: "json" (gated by LoggingBetaOptions), "text". (default "text")