feat[venom]: "pickaxe" stack scheduler optimization

[charles-cooper]

What I did

fix for #3950

How I did it

How to verify it

Commit message

implement "pickaxe" stack scheduler optimization.

sometimes, venom produces some unneeded stack traffic. this can't be
fixed by improved dataflow analysis, because it is an issue in the stack
scheduler rather than instruction reordering. what happens is a stack
item is produced, but it has a longer lifespan than other things on the
stack and the instruction cannot be reordered. this commit introduces a
simple heuristic: at the time of stack item production, check the live
list for something with "shorter" liveness we can swap it with.

i just made up the "pickaxe" term but i think it sounds cool :)

Description for the changelog

Cute Animal Picture

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.95%. Comparing base (ac19367) to head (169506a).
Report is 1 commits behind head on master.

❗ Current head 169506a differs from pull request most recent head 9b54c4e

Please upload reports for the commit 9b54c4e to get more accurate results.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3951      +/-   ##
==========================================
- Coverage   91.02%   87.95%   -3.07%     
==========================================
  Files         106      106              
  Lines       15306    15309       +3     
  Branches     3370     3365       -5     
==========================================
- Hits        13932    13465     -467     
- Misses        935     1307     +372     
- Partials      439      537      +98     

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[charles-cooper]

this improves codesize between 0.5%-1% on some test contracts i have