Replace kompose.image-pull-policy with compose's pull_policy

[kominoshja]

What would you like to be added?

Back in #1052, compose didn't support a pull_policy property, so kompose.image-pull-policy label was added, however since then, compose does have pull_policy and therefore we can construct ImagePullPolicy from pull_policy

Why is this needed?

To avoid redundant labels and confusing issues with defining ImagePullPolicy

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/lifecycle stale

[kominoshja]

/remove-lifecycle stale