perf[venom]: improve CSE elimination speed

[charles-cooper]

What I did

avoid O(n*k) (n==number of instructions, k==number of available expressions) copies by replacing the dict with a HAMT. HAMT is an immutable dict with O(1) copy (copy by reference), and O(log N) insert/delete/update operations.

also use lru_cache for some Flag operations (which are bizarrely a perf hotspot)

How I did it

How to verify it

Commit message

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Description for the changelog

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[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	immutables@​0.21

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.46%. Comparing base (f2cb6c2) to head (57ffa2c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4607      +/-   ##
==========================================
+ Coverage   92.44%   92.46%   +0.01%     
==========================================
  Files         127      127              
  Lines       18308    18321      +13     
  Branches     3174     3173       -1     
==========================================
+ Hits        16925    16940      +15     
+ Misses        946      945       -1     
+ Partials      437      436       -1     

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