CONTRACTS: add missing source locations

[remi-delmas-3000]

Adds missing source locations on instrumentation instructions.

• 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.
• 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).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.06% ⚠️

Comparison is base (08a466d) 78.80% compared to head (d01248a) 78.74%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7850      +/-   ##
===========================================
- Coverage    78.80%   78.74%   -0.06%     
===========================================
  Files         1699     1699              
  Lines       195104   195105       +1     
===========================================
- Hits        153756   153645     -111     
- Misses       41348    41460     +112     

Files Changed	Coverage Δ
.../contracts/dynamic-frames/dfcc_instrument_loop.cpp	99.61% <100.00%> (ø)
...t/contracts/dynamic-frames/dfcc_spec_functions.cpp	92.16% <100.00%> (+0.04%)	⬆️

... and 9 files with indirect coverage changes

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