Add support for json logging format

[madufresneelastic]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Add support for structured logging with --logging-format that is already supported by many kubernetes components.

Which issue(s) this PR fixes:

Fixes #
#5898

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Add structured logging support via `--logging-format json`

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

[Other doc]: https://kubernetes.io/blog/2020/09/04/kubernetes-1-19-introducing-structured-logs/

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• ✅ login: madufresneelastic / name: Marc-Andre Dufresne (55c92e1)

[madufresneelastic]

/retest

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[madufresneelastic]

/assign towca

[mwielgus]

Can you add some documetation/FAQ entry as well?

[madufresneelastic]

Can you add some documetation/FAQ entry as well?

I added an FAQ entry, is this enough or there should be additional documentation somewhere else?

[mwielgus]

Please squash the commits to 1 (currently there is 11) and we are good to go.

[madufresneelastic]

@mwielgus as discussed, commits are squashed. I just pushed another one (still squashed). I had missed that imports were not sorted properly, this is now fixed.

[mwielgus]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: madufresneelastic, mwielgus

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[grosser]

I picked this single commit to get json logging since it's not yet released and it broke --leader-elect-lease-duration not sure why

5bcb526e0 Kubernetes Prow Robot 3 months ago  (tag: cluster-autoscaler-1.28.0)
2b980eddd Marc-Andre Dufresne 3 months ago add json logging support
go build -o cluster-autoscaler-arm64 --ldflags "-s"
./cluster-autoscaler-arm64 --leader-elect-lease-duration 1s
unknown flag: --leader-elect-lease-duration

works before, breaks after 😞