Adjust proof tooling to support CBMC v6

[tautschnig]

Description

With CBMC v6, unwinding assertions are enabled by default, and object bits no longer need to be set at compile time. Update various build rules to use the latest template as provided with CBMC starter kit.

Test Steps

Tested in CI.

Checklist:

• [ ] I have tested my changes. No regression in existing tests.
• n/a I have modified and/or added unit-tests to cover the code changes in this Pull Request.

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.66%. Comparing base (e0cd4db) to head (41cbc24). Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #200      +/-   ##
==========================================
+ Coverage   94.02%   96.66%   +2.64%     
==========================================
  Files           3        3              
  Lines        1690     1680      -10     
  Branches      442      443       +1     
==========================================
+ Hits         1589     1624      +35     
+ Misses         17        0      -17     
+ Partials       84       56      -28     

Flag	Coverage Δ
unit_tests	96.66% <ø> (+2.64%)	:arrow_up:

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