Support structured logging

[bells17]

What type of PR is this?

/kind feature

What this PR does / why we need it:

I've updated the klog functions used within csi-lib-utils to structured logging functions, following the guidelines below:
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-instrumentation/migration-to-structured-logging.md

Several CSI Sidecars like external-snapshotter rely on csi-lib-utils, and to fully support structured logging in these Sidecars, it's necessary for csi-lib-utils to adopt structured logging as well.

In addition, I've modified the log messages based on the following guideline:
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-instrumentation/migration-to-structured-logging.md#remove-string-formatting-from-log-message

I’ve updated the klog functions in use according to the guidelines provided below, and I've confirmed that they pass the logcheck tests:
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-instrumentation/migration-to-structured-logging.md#change-log-functions

Which issue(s) this PR fixes:

Fixes #150

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Added support for structured logging (the log messages have been changed due to the activation of structured logging)

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
If you want CI signal for your change, please convert it to an actual PR.
You can still manually trigger a test run with /test all

[pohly]

Instead of "just" doing structured logging, would it be possible to also do contextual logging, i.e. remove the dependency on the global logger?

This makes libraries more versatile.

[bells17]

@pohly Thank you for your review.

Instead of "just" doing structured logging, would it be possible to also do contextual logging, i.e. remove the dependency on the global logger?

This makes libraries more versatile.

I've made an attempt to incorporate contextual logging as well. Could you please review it again?
(Sorry for the inconvenience, I had to force push due to a failed conflict resolution.)

I have also confirmed that the following tests with logcheck pass:

$ logcheck -check-contextual ./accessmodes/
$ logcheck -check-contextual ./connection/
$ logcheck -check-contextual ./deprecatedflags/
$ logcheck -check-contextual ./leaderelection/
$ logcheck -check-contextual ./metrics/
$ logcheck -check-contextual ./protosanitizer/
$ logcheck -check-contextual ./rpc/

[bells17]

@pohly Thank you for the review.
I've made revisions following the comments you provided. I would appreciate it if you could confirm the changes.

[pohly]

Some small nits, but overall this looks good.

[bells17]

@pohly Thank you for the improvement suggestions. I've updated the implementation accordingly.
Could you please review the changes when you have a moment?

[pohly]

/lgtm

@bells17: can you squash into one commit?

[bells17]

@pohly Thank you for the review and lgtm!
I've squashed the commits into one.

[pohly]

/lgtm
/assign @jsafrane

For approval.

[jsafrane]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bells17, jsafrane

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