speedup hash_of_block function

[flc666star]

The current time complexity of the hash_of_block function is O(n^2). This PR aimed to optimize it to O(n) by including the hash of the predecessor block in the calculation, in addition to the tokens of current block when calculating its hash.

[github-actions]

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[DarkLight1337]

Can you check whether this is still necessary with the introduction of block_manager_v2?

[comaniac]

Can you check whether this is still necessary with the introduction of block_manager_v2?

Echo on this. As we plan to deprecate block manager v1 in a few week, it would be better to focus on block manager v2. Also cc @sroy745 @rickyyx as you may be interested in this.