Add overflow_result_exprt: compute result and overflow in one expression

[tautschnig]

Doing both the arithmetic operation and determining whether or not there
was an overflow previously required either multiple expressions or going
via __builtin_X_overflow, which should be specific to the C front-end.

The new expression returns a struct with two components, the first of
which has the type of the arithmetic operation, and the second is
Boolean.

Fixes: #6841

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• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6903 (5ea97b3) into develop (577b0ec) will decrease coverage by 0.04%.
The diff coverage is 54.08%.

@@             Coverage Diff             @@
##           develop    #6903      +/-   ##
===========================================
- Coverage    77.81%   77.77%   -0.05%     
===========================================
  Files         1568     1568              
  Lines       179975   180315     +340     
===========================================
+ Hits        140044   140234     +190     
- Misses       39931    40081     +150     

Impacted Files	Coverage Δ
src/solvers/flattening/boolbv.h	62.50% <ø> (ø)
src/util/bitvector_expr.cpp	58.55% <0.00%> (-35.65%)	⬇️
src/util/simplify_expr_class.h	90.47% <ø> (ø)
src/solvers/flattening/boolbv_overflow.cpp	43.94% <35.65%> (-4.74%)	⬇️
src/util/simplify_expr.cpp	83.08% <51.37%> (-2.66%)	⬇️
src/solvers/smt2/smt2_conv.cpp	67.39% <57.14%> (+0.13%)	⬆️
.../goto-instrument/goto_instrument_parse_options.cpp	70.90% <73.33%> (-0.23%)	⬇️
src/goto-programs/goto_convert_side_effect.cpp	95.13% <94.59%> (-0.41%)	⬇️
src/ansi-c/c_typecheck_base.cpp	81.15% <95.23%> (+2.27%)	⬆️
src/util/bitvector_expr.h	97.24% <95.65%> (-0.10%)	⬇️
... and 12 more

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