Simplify byte_extract(byte_update(...)) without overlap

[tautschnig]

When extracting bytes not affected by an inner update the extract can directly refer to the object subject to the update.

• 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.

[codecov]

Codecov Report

Base: 77.99% // Head: 78.00% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (adee8c6) compared to base (9d51ea2).
Patch coverage: 92.42% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop    #7251    +/-   ##
=========================================
  Coverage    77.99%   78.00%            
=========================================
  Files         1619     1621     +2     
  Lines       187194   187297   +103     
=========================================
+ Hits        146007   146102    +95     
- Misses       41187    41195     +8     

Impacted Files	Coverage Δ
src/cprover/console.cpp	29.06% <0.00%> (-2.19%)	⬇️
src/cprover/console.h	66.66% <ø> (ø)
src/cprover/cprover_parse_options.cpp	56.58% <0.00%> (ø)
src/goto-programs/goto_trace.cpp	81.41% <ø> (ø)
unit/util/expr_cast/expr_cast.cpp	100.00% <ø> (ø)
src/solvers/flattening/boolbv_byte_extract.cpp	69.73% <75.00%> (-0.40%)	⬇️
src/cprover/solver_progress.cpp	80.00% <80.00%> (ø)
src/util/pointer_offset_size.cpp	92.72% <83.72%> (-0.12%)	⬇️
src/util/simplify_expr.cpp	83.90% <92.85%> (+0.12%)	⬆️
...de/java_trace_validation/java_trace_validation.cpp	100.00% <100.00%> (ø)
... and 18 more

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[peterschrammel]

A test would be good.

[tautschnig]

A test would be good.

Same here: I believe union field sensitivity will take care of this.