feat: Enhanced StateDB logs for Concurrency Safety

[matthew-alexander-partior]

Problem

During execution such as simulation calls, Quorum attempts to copy the state trie from stateDb.go via a goroutine, this involves copying the logs mapping from stateDb

Inside the stateDb Copy() function, it acquires a mutex but releases it just before copying the logs mapping which was introduced in this [PR] https://github.com/Consensys/quorum/pull/1331/files#diff-c3757dc9e9d868f63bc84a0cc67159c1d5c22cc5d8c9468757098f0492e0658c)

With no guard in place for logs mapping, we experienced a race condition when accessing & writing to logs as seen below

fatal error: concurrent map iteration and map write

goroutine 22214 [running]:
github.com/ethereum/go-ethereum/core/state.(*StateDB).Copy(0xc000f216c0)
	github.com/ethereum/go-ethereum/core/state/statedb.go:869 +0xae5

Solution

This PR replaces logs implementation of map with sync.Map to ensure accessing / modifying logs is done in a concurrency safe manner