feat: KVBM Cache Hit events

[jthomson04]

• Adds KV Cache hit events
• Restructures events to include an enum of event type.
• Refactors event management logic to accept a list of event managers, instead of a single one
• Also includes a PoC of cache-hit-aware block management, where blocks with more cache hits are prioritized for retention and offloading

[copy-pr-bot]

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