Simplify goto-program generated for short-circuit operators

[kroening]

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[codecov]

Codecov Report

Merging #7051 (318ddb3) into develop (438aad3) will decrease coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 318ddb3 differs from pull request most recent head 1570e0a. Consider uploading reports for the commit 1570e0a to get more accurate results

@@             Coverage Diff             @@
##           develop    #7051      +/-   ##
===========================================
- Coverage    77.88%   77.86%   -0.03%     
===========================================
  Files         1569     1569              
  Lines       180989   180996       +7     
===========================================
- Hits        140962   140924      -38     
- Misses       40027    40072      +45     

Impacted Files	Coverage Δ
src/goto-programs/goto_clean_expr.cpp	99.02% <100.00%> (-0.50%)	⬇️
src/goto-programs/goto_convert_class.h	88.15% <100.00%> (+0.32%)	⬆️
src/goto-programs/goto_convert_side_effect.cpp	94.47% <100.00%> (-0.67%)	⬇️
src/goto-programs/goto_convert.cpp	88.12% <0.00%> (-4.22%)	⬇️
src/solvers/flattening/boolbv_quantifier.cpp	89.91% <0.00%> (-3.37%)	⬇️
src/ansi-c/goto_check_c.cpp	91.65% <0.00%> (+0.09%)	⬆️

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[jimgrundy]

Looks like there are three places where we used to replace an index/dereference with a temporary and now we don't. It would make it all much clearer for me if you could give a small code snippet example of each of the three cases.