add tolerations option for building image with kaniko

[GwonsooLee]

Fixes: #nnn

Description
When building image with kaniko, kaniko pod cannot be scheduled if all nodes are tainted for management issue. Tolerations is common kubernetes pod option so that, even though there is no issue published related to this, it would be helpful if this feature in on.

User facing changes (remove if N/A)
Yes, when to use kaniko with tainted node

Follow-up Work (remove if N/A)

• Add Tolerations feature in cluster_detail

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[GwonsooLee]

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[codecov]

Codecov Report

Merging #4256 into master will decrease coverage by 0.01%.
The diff coverage is 100.00%.

Impacted Files	Coverage Δ
pkg/skaffold/schema/latest/config.go	100.00% <ø> (ø)
pkg/skaffold/build/cluster/pod.go	87.50% <100.00%> (+0.14%)	⬆️
...affold/kubernetes/portforward/kubectl_forwarder.go	60.97% <0.00%> (-2.44%)	⬇️

[briandealwis]

One minor nit

[briandealwis]

Suggested change

	# If kaniko pod should be run on the tainted node, You can setup tolerations here.
	# If kaniko pod should be run on a tainted node, you can setup tolerations here.

[tejal29]

LGTM except minor nit.

[GwonsooLee]

@briandealwis @tejal29 Thanks for review. I fix the minor nit :)

[briandealwis]

Thanks!