goto-instrument/unwinding: enable unwinding assertions by default

[tautschnig]

This will make behaviour consistent (and sound-by-default) across CBMC and goto-instrument.

• 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.
• 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.

[martin-cs]

"Consistent" and "sound-by-default" are things I love to see in a PR.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.78%. Comparing base (ae7d311) to head (900acce).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8274      +/-   ##
===========================================
- Coverage    77.81%   77.78%   -0.04%     
===========================================
  Files         1721     1721              
  Lines       189460   189536      +76     
  Branches     18401    18401              
===========================================
+ Hits        147432   147434       +2     
- Misses       42028    42102      +74     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.