drop managed fields from audit entries

[tkashem]

What type of PR is this?

/kind feature

What this PR does / why we need it:
Implements kubernetes/enhancements#2982

This PR adds a new field OmitManagedFields to both audit.Policy and audit.PolicyRule so cluster operators can opt in to omit managed fields of the request and response bodies from being written to the API audit log.

Does this PR introduce a user-facing change?:

A new field `omitManagedFields` has been added to both `audit.Policy` and `audit.PolicyRule` 
so cluster operators can opt in to omit managed fields of the request and response bodies from 
being written to the API audit log.

[k8s-ci-robot]

Hi @tkashem. Thanks for your PR.

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[tkashem]

/assign @sttts

[tkashem]

API changes have been made according to the KEP - kubernetes/enhancements#2982. This is ready for another pass.

@wojtek-t @apelisse @sttts

[sttts]

/hold cancel

as discussed, KEP update has been done

[sttts]

/lgtm
/approve

[sttts]

/assign @liggitt

for API approval.

[liggitt]

audit policy config lgtm

[liggitt]

do we know the relative cost (cpu/allocs) of adding a deep copy into the audit pipeline by enabling the omitManagedFields option globally?

[tkashem]

@liggitt @sttts I added an empty TableRow object to my test to cover the nil case. that's the only change.

[liggitt]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: liggitt, sttts, tkashem

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Needs approval from an approver in each of these files:

• staging/src/k8s.io/apiserver/OWNERS [liggitt,sttts]
• staging/src/k8s.io/apiserver/pkg/apis/OWNERS [liggitt]

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[sttts]

/lgtm