Fix basic block coverage with unsatisfiable ASSUME statements

[tautschnig]

Insert coverage assertions at the end of basic blocks instead of the beginning to ensure blocks are only marked as covered when all instructions, including ASSUME statements, can be executed.

Fixes: #826

• 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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.93%. Comparing base (4fe3ade) to head (d5cab1c).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8791   +/-   ##
========================================
  Coverage    79.93%   79.93%           
========================================
  Files         1698     1698           
  Lines       187698   187698           
  Branches        73       73           
========================================
  Hits        150034   150034           
  Misses       37664    37664           

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[tautschnig]

Closing as this was already taking care of in #7810.