core: Simplify the pattern rewriter

[math-fehr]

Now that the pattern rewriter use the worklist, it is not necessary to keep track of the inserted operations before/after
the matched operation.
We can thus remove all these checks.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (e6ca26f) 89.94% compared to head (21a2af8) 89.99%.

Files	Patch %	Lines
xdsl/pattern_rewriter.py	71.42%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1910      +/-   ##
==========================================
+ Coverage   89.94%   89.99%   +0.05%     
==========================================
  Files         287      287              
  Lines       35779    35664     -115     
  Branches     5266     5242      -24     
==========================================
- Hits        32181    32097      -84     
+ Misses       2838     2816      -22     
+ Partials      760      751       -9     

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[superlopuh]

beautiful

[webmiche]

Could you rebase this? I think that would make it more reviewable :)

[webmiche]

Now that actually looks like a simplification 😉

I still wonder if no downstream users are affected (in particular in the Chocopy world), but if we can make sure it's fine, I think this is a good change 👍