feat: batch hash

[twoeths]

Motivation

• for a common x86_64 server in our infrastructure, it's 1.8x faster to batch hash so we should find a way to utilize it
• for Mac Silicon, batch hash is not really faster (see [hashtree-z] batch hash performance in aarch64 hashtree-z#7). However this implementation shows it's 10% faster than recursive hash consistently so we should use batch hash too

Descriptions

• new batch hash api in pool
  • use a lazy_nodes ArrayList to store nodes at different levels to hash bottom-up
  • track start index of each level in a stack-allocated array and populate it along the way