XML counterexample trace: display member types

[tautschnig]

Field-sensitive SSA yields assignments at member/element level. The XML
counterexamples, however, appeared to (continue to) assume that all
assignments take place at object level. Adjust the type (which is only
included in XML output, not in JSON nor plain output) to match that of
the element being assigned.

• 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

Merging #6869 (6d7269d) into develop (bcca9da) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6869      +/-   ##
===========================================
- Coverage    77.80%   77.80%   -0.01%     
===========================================
  Files         1567     1567              
  Lines       179916   179917       +1     
===========================================
  Hits        139988   139988              
- Misses       39928    39929       +1     

Impacted Files	Coverage Δ
src/goto-programs/xml_goto_trace.cpp	99.41% <100.00%> (+<0.01%)	⬆️
src/ansi-c/expr2c.cpp	67.58% <0.00%> (-0.05%)	⬇️

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[kroening]

Would it make sense to call that full_lhs_type, to avoid ambiguity?

[tautschnig]

Would it make sense to call that full_lhs_type, to avoid ambiguity?

Done.

[peterschrammel]

@TGWDB ^ Change in the XML specification