Simplify byte extract: use lowering when expression is a constant

[tautschnig]

When none of the earlier simplification rules apply, rewrite the expression to to apply simplification rules for arithmetic and logic expressions.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a 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.

[feliperodri]

@tautschnig #7331 got merged, so this PR should be ready for a rebase before going through review.

[codecov]

Codecov Report

Base: 78.37% // Head: 78.39% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (7c2fa6f) compared to base (941030e).
Patch coverage: 93.39% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7340      +/-   ##
===========================================
+ Coverage    78.37%   78.39%   +0.01%     
===========================================
  Files         1647     1647              
  Lines       190328   190362      +34     
===========================================
+ Hits        149172   149226      +54     
+ Misses       41156    41136      -20     

Impacted Files	Coverage Δ
src/analyses/constant_propagator.h	82.35% <ø> (ø)
src/ansi-c/expr2c.cpp	67.66% <ø> (+0.42%)	⬆️
src/goto-instrument/havoc_loops.cpp	0.00% <0.00%> (ø)
src/util/pointer_predicates.cpp	95.12% <ø> (+2.39%)	⬆️
src/util/pointer_predicates.h	100.00% <ø> (ø)
src/util/simplify_expr_class.h	90.47% <ø> (ø)
src/util/simplify_expr_pointer.cpp	86.58% <ø> (+0.75%)	⬆️
src/analyses/constant_propagator.cpp	95.46% <88.88%> (ø)
src/util/expr_util.cpp	90.55% <95.83%> (+0.81%)	⬆️
src/ansi-c/c_typecheck_expr.cpp	75.60% <100.00%> (ø)
... and 20 more

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