Byte extract lowering: refactor lowering of arrays/vectors [blocks: #6488]

[tautschnig]

Both cases had some of the same code. Refactor those cases out of an
already-too-big function into one of its own.

This is in preparation of further changes to this code to support some
of the cases currently deemed unsupported.

• Each commit message has a non-empty body, explaining why the change was made.
• 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

Merging #6486 (bee3b76) into develop (5bf69a3) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6486      +/-   ##
===========================================
- Coverage    76.04%   76.03%   -0.01%     
===========================================
  Files         1546     1546              
  Lines       165521   165511      -10     
===========================================
- Hits        125864   125854      -10     
  Misses       39657    39657              

Impacted Files	Coverage Δ
src/solvers/lowering/byte_operators.cpp	92.14% <100.00%> (-0.08%)	⬇️

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[martin-cs]

I think this is fine to merge even though there is a minor drop in coverage.

[tautschnig]

I think this is fine to merge even though there is a minor drop in coverage.

Fair, but I'm patting myself on the back for 100% patch coverage 😇