Fix support for with_exprt with more than 3 operands

[tautschnig]

A with_exprt needs to have at least 3 operands, but can encode multiple updates when using more operands (where any further operands need to come in pairs of two: an index/member and a new value). We already support this in several places, but were still missing support in others. This led to wrong verification results in Kani as recent changes in CBMC make increasing use of the value set (which is among those fixed in this commit).

• 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

Attention: Patch coverage is 49.29577% with 36 lines in your changes missing coverage. Please review.

Project coverage is 80.39%. Comparing base (5d1438a) to head (ebbbccb).

Files with missing lines	Patch %	Lines
src/goto-programs/interpreter_evaluate.cpp	0.00%	17 Missing ⚠️
src/pointer-analysis/value_set_fi.cpp	0.00%	10 Missing ⚠️
src/solvers/smt2/smt2_format.cpp	0.00%	6 Missing ⚠️
src/pointer-analysis/value_set.cpp	90.62%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8668      +/-   ##
===========================================
- Coverage    80.39%   80.39%   -0.01%     
===========================================
  Files         1688     1688              
  Lines       207391   207414      +23     
  Branches        73       73              
===========================================
+ Hits        166730   166746      +16     
- Misses       40661    40668       +7     

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[rod-chapman]

Test results for mlkem-native/main, mldsa-native/main and mldsa-native/remove_8617 are all good.