Add PodDisruptionBudget metrics

[gregory-lyons]

What this PR does / why we need it:
Adds metrics for PodDisruptionBudget

Which issue(s) this PR fixes :
Fixes #546

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[gregory-lyons]

anyone get a chance to look at this?

[brancz]

Did you have a chat with @mxinden about rebasing this on top of his in-progress architecture changes?

[gregory-lyons]

I mentioned it here: #546 (comment)

If the architecture changes are close to merge, I can rebase. @mxinden what's the current status?

[mxinden]

@gregory-lyons #534 merged today. Let me know if I can help you adapting to the changes. I a sorry for the inconvenience.

[gregory-lyons]

@mxinden @brancz I've now rebased on top of #534

[brancz]

/lgtm sorry for the delay, and thanks for bearing with us :)

[mxinden]

I will follow up fixing the TODO comments in general for all collectors. Thanks for rebasing!

[gregory-lyons]

@brancz anything else I need to do on my end to get this merged? Thanks for review

[brancz]

Actually not sure why it didn’t merge it.

/approve
/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: brancz, gregory-lyons

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