core: Fix bug in pattern rewriter when ErasedSSAValue is present

[math-fehr]

When an operation is deleted, the pattern rewriter adds its operands with 1 use to the worklist of operations to change.
This change checks that these operands are not ErasedSSAValue, otherwise an erased operation would be added to the worklist.

I'm starting to think that the ErasedSSAValue design is bad, I'll be thinking of a way to change this.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.60%. Comparing base (836098f) to head (6dc5fe8).
Report is 106 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2365      +/-   ##
==========================================
+ Coverage   89.48%   89.60%   +0.12%     
==========================================
  Files         326      345      +19     
  Lines       38825    40700    +1875     
  Branches     5744     6051     +307     
==========================================
+ Hits        34741    36471    +1730     
- Misses       3286     3352      +66     
- Partials      798      877      +79     

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