1. Use layered natives cache. With layered cache the storeblock
process includes the following steps: create a wrapper over
current nativeCache, put changes into upper nativeCache layer,
persist (or discard) changes.
2. Split contract getters to read-only and read-and-change. Read-only
ones doesn't require the copy of an existing nativeCache item.
Read-and-change ones create a copy and after that change the copy.
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