Fix snapshots to respect buffered deletes on get

[krishnangovindraj]

Usage and product changes

We fix a bug where the get operation on snapshots would treat a buffered delete as an absent key. Usages of it would then fall back to storage and find the key..

Usage and product changes

• Make usages of snapshot.get explicitly handle deletes.
• Add test checking deletes of committed keys are seen by the deleting snapshot

[vaticle-bot]

PR Review Checklist

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Trivial Change

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Code

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