Release CBMC 6.5.0

[tautschnig]

This release addresses both soundness (via #8562) and performance issues (via
#8574, #8576) in our code contracts instrumentation, and includes a collection
of bit-operator cleanup (such as #8524, #8531) and floating-point support improvements (TiesToAway rounding via #8515, native rounding to integer via
#8538) that aid EBMC/HW-CBMC.

• 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.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.17%. Comparing base (e033ba1) to head (d52b560).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8607   +/-   ##
========================================
  Coverage    79.17%   79.17%           
========================================
  Files         1733     1733           
  Lines       198963   198963           
  Branches     17967    17967           
========================================
  Hits        157536   157536           
  Misses       41427    41427           

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