core/state: fix concurrent map read and write for stateUpdate.accounts

[buddh0]

Description

core/state: fix concurrent map read and write for stateUpdate.accounts

Rationale

v1.5.7 crashed via log

Example

read path is as shown in the above picture
write path:

  commitAndFlush
  	-->err := snap.Cap(ret.root, snap.CapLimit())
  		-->persisted := t.cap(diff, layers)
  			-->flattened := parent.flatten().(*diffLayer)
  				-->	for hash, data := range dl.accountData {
  					parent.accountData[hash] = data
  					}

Changes

Notable changes:

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