fix: staking cache to in-memory KV store

[randy-cro]

Description

This PR fixes inconsistencies in the staking cache (originally implemented in PR #1725) across different nodes.
Previously, simulation or optimistic execution contexts did not properly handle discarded changes, which could lead to duplicate or incorrect cache data, eventually causing apphash mismatches and halting the chain.

The primary change refactors the cache to use an in-memory KV store.
With this approach, when a context is discarded, the cache is automatically rolled back, just like any other store in the system.

This ensures that cache state remains consistent with the underlying store, even during simulations or optimistic execution scenarios.

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[randy-cro]

Member

@songgaoye it is here, did u miss it?