Update Snapshoting to use hierarchy.Manager

[gabesaba]

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

This change simplifies edge management in the Snapshot. This will allow us, in a simple manner, to snapshot and create edges between HierarchicalCohorts (#79) in a subsequent PR.

Special notes for your reviewer:

Hide ws diff when reviewing snapshot_test.go

Does this PR introduce a user-facing change?

NONE

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[gabesaba]

/assign @mimowo

[mimowo]

This looks like a flake: https://prow.k8s.io/view/gs/kubernetes-jenkins/pr-logs/pull/kubernetes-sigs_kueue/2989/pull-kueue-test-e2e-main-1-31/1831630396710719488. Please open an issue.

[gabesaba]

This looks like a flake: https://prow.k8s.io/view/gs/kubernetes-jenkins/pr-logs/pull/kubernetes-sigs_kueue/2989/pull-kueue-test-e2e-main-1-31/1831630396710719488. Please open an issue.

#2990
/retest

[mimowo]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 45e189ef66e85060d2f2cae6b3fa59323197a29c

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gabesaba, mimowo

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