Remove support for vector-typed expressions from back-ends

[tautschnig]

The semantics of these are prescribed by GCC and we rightly rewrite them by remove_vector at GOTO-program level. Given this rewriting, any existing support in back-ends was untested and likely incomplete (or possibly broken).

This is, therefore, a removal of unused code.

• 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

Patch coverage: 83.33% and project coverage change: +0.07 🎉

Comparison is base (d5e13f1) 78.54% compared to head (70a95a8) 78.62%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7736      +/-   ##
===========================================
+ Coverage    78.54%   78.62%   +0.07%     
===========================================
  Files         1688     1687       -1     
  Lines       193001   192809     -192     
===========================================
- Hits        151599   151588      -11     
+ Misses       41402    41221     -181     

Impacted Files	Coverage Δ
src/solvers/flattening/boolbv.cpp	87.38% <ø> (+0.22%)	⬆️
src/solvers/flattening/boolbv.h	62.50% <ø> (ø)
src/solvers/flattening/boolbv_floatbv_op.cpp	61.95% <0.00%> (ø)
src/solvers/flattening/boolbv_get.cpp	89.17% <ø> (+5.92%)	⬆️
src/solvers/flattening/boolbv_width.cpp	79.31% <ø> (+5.50%)	⬆️
src/solvers/flattening/boolbv_add_sub.cpp	50.00% <84.61%> (+1.72%)	⬆️
src/solvers/flattening/boolbv_unary_minus.cpp	45.45% <100.00%> (+1.33%)	⬆️
src/solvers/smt2/smt2_conv.cpp	70.26% <100.00%> (+2.88%)	⬆️

... and 1 file with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[TGWDB]

Approving on the basis that we believe that vectors should be removed by this point and this code looks like it will (typically) error out when an ID_vector appears somewhere unexpected. I'd feel safer if we had the checks for symex-ready-goto in place though.

[tautschnig]

Approving on the basis that we believe that vectors should be removed by this point and this code looks like it will (typically) error out when an ID_vector appears somewhere unexpected. I'd feel safer if we had the checks for symex-ready-goto in place though.

Thank you for noting that down in #7695!