Simplifier: do not create extractbits with pointer type

[tautschnig]

This is a fix-up for 525c23d: we must not remove typecasts towards pointers when the operand is extractbits as our back-ends do not support extractbits with pointer type.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.39%. Comparing base (062962c) to head (a7e7d83).
Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8678      +/-   ##
===========================================
- Coverage    80.39%   80.39%   -0.01%     
===========================================
  Files         1688     1688              
  Lines       207383   207384       +1     
  Branches        73       73              
===========================================
- Hits        166731   166729       -2     
- Misses       40652    40655       +3     

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