core: write head block hash when shutdown

[NathanBSC]

Description

core: write head block hash when shutdown

Rationale

1. without write down head block hash, prune state may get error as following

WARN [10-10|08:59:59.106] Failed to load snapshot                  err="head doesn't match snapshot: have 0x386c55a45a2dc49e8152eb7e43843edffae9214e3bb7d3a50224b11a3f62e9b0, want 0x11968cf7a00e02b1cfd477f8d39c17871d54cfce0b60c24b207ad23a782e3222"
ERROR[10-10|08:59:59.107] Failed to open snapshot tree             err="head doesn't match snapshot: have 0x386c55a45a2dc49e8152eb7e43843edffae9214e3bb7d3a50224b11a3f62e9b0, want 0x11968cf7a00e02b1cfd477f8d39c17871d54cfce0b60c24b207ad23a782e3222"

2. when run triedb.Dereference in a go routine, may report error in log

Dangling trie nodes after full cleanup

Example

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Changes

Notable changes:

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