Introduce bitst and bytest to avoid bit/byte mix-up

[tautschnig]

Use mp_integers with a unit to clarify when an mp_integer holds a number
of bits or a number of bytes. This makes sure that type-inconsistent
comparisons as fixed in #7411 result in compile-time errors.

• 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

Attention: Patch coverage is 91.94396% with 46 lines in your changes missing coverage. Please review.

Project coverage is 78.36%. Comparing base (2ffc4c9) to head (b533d00).

Files	Patch %	Lines
src/cprover/bv_pointers_wide.cpp	55.55%	8 Missing ⚠️
src/goto-programs/interpreter_evaluate.cpp	33.33%	6 Missing ⚠️
src/solvers/flattening/bv_pointers.cpp	73.33%	4 Missing ⚠️
src/util/pointer_offset_size.cpp	91.66%	4 Missing ⚠️
src/ansi-c/expr2c.cpp	25.00%	3 Missing ⚠️
src/ansi-c/padding.cpp	93.87%	3 Missing ⚠️
src/pointer-analysis/value_set.cpp	80.00%	3 Missing ⚠️
src/analyses/goto_rw.cpp	77.77%	2 Missing ⚠️
src/goto-synthesizer/cegis_evaluator.cpp	60.00%	2 Missing ⚠️
src/memory-analyzer/analyze_symbol.cpp	89.47%	2 Missing ⚠️
... and 8 more

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7413      +/-   ##
===========================================
+ Coverage    78.09%   78.36%   +0.27%     
===========================================
  Files         1726     1727       +1     
  Lines       189039   188491     -548     
  Branches     18399    18442      +43     
===========================================
+ Hits        147629   147717      +88     
+ Misses       41410    40774     -636     

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[thomasspriggs]

Have you seen the approach taken to strong types here? https://www.fluentcpp.com/2016/12/08/strong-types-for-strong-interfaces/

This approach appears to have the following advantages -

• Templates are used to avoid needing a full cut-and-paste definition for each of the strong / unit associated types.
• Values are stored using containership rather than inheritance. This could side-step some of the potential issues with implicit upcasting.

[tautschnig]

Have you seen the approach taken to strong types here? https://www.fluentcpp.com/2016/12/08/strong-types-for-strong-interfaces/

This approach appears to have the following advantages -

* Templates are used to avoid needing a full cut-and-paste definition for each of the strong / unit associated types.

* Values are stored using containership rather than inheritance. This could side-step some of the potential issues with implicit upcasting.

Thank you for alerting me to this! This will require implementing more methods, but that's ok. I'll try this route.

[feliperodri]

LGTM.