feat[ir]: add sanity check

[charles-cooper]

What I did

add a stronger sieve for duplicated IRnodes

How I did it

How to verify it

Commit message

Commit message for the final, squashed PR. (Optional, but reviewers will appreciate it! Please see our commit message style guide for what we would ideally like to see in a commit message.)

Description for the changelog

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 90.47619% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 51.85%. Comparing base (f0afaf0) to head (0cad92e).
Report is 1 commits behind head on master.

Files	Patch %	Lines
vyper/ir/compile_ir.py	75.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #3862       +/-   ##
===========================================
- Coverage   91.12%   51.85%   -39.27%     
===========================================
  Files         106      106               
  Lines       15308    15329       +21     
  Branches     3365     3369        +4     
===========================================
- Hits        13949     7949     -6000     
- Misses        925     6807     +5882     
- Partials      434      573      +139     

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