Linking/static lifetime init: do not use goto code types

[tautschnig]

The code in src/linking supposedly deals with symbol tables only, not
with goto programs (goto-programs/link_goto_model does this).
Consequently, static lifetime init should not create codet structures
defined in goto-programs/goto_instruction_code.h.

This is a first step to remove the goto-programs dependency from
src/linking.

• 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 #6554 (13d86b0) into develop (7965ba2) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #6554      +/-   ##
===========================================
- Coverage    76.64%   76.64%   -0.01%     
===========================================
  Files         1579     1579              
  Lines       181479   181476       -3     
===========================================
- Hits        139101   139098       -3     
  Misses       42378    42378              

Impacted Files	Coverage Δ
src/linking/static_lifetime_init.cpp	98.63% <100.00%> (-0.06%)	⬇️

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[chris-ryder]

Good catch!