Factor out re-creating __CPROVER_initialize into a function

[tautschnig]

This avoids repeating the almost-same code in several places, and moves
a helper that is not DFCC-specific to the global context.

The first two commits are #7678 and #7679.

• 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.
• 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: 100.00% and project coverage change: -0.01 ⚠️

Comparison is base (ba47c86) 78.55% compared to head (1909f3e) 78.55%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7680      +/-   ##
===========================================
- Coverage    78.55%   78.55%   -0.01%     
===========================================
  Files         1686     1686              
  Lines       192923   192897      -26     
===========================================
- Hits        151552   151526      -26     
  Misses       41371    41371              

Impacted Files	Coverage Δ
...instrument/contracts/dynamic-frames/dfcc_utils.cpp	89.57% <ø> (-0.36%)	⬇️
...o-instrument/contracts/dynamic-frames/dfcc_utils.h	100.00% <ø> (ø)
src/goto-cc/linker_script_merge.cpp	78.16% <100.00%> (-0.38%)	⬇️
.../goto-instrument/contracts/dynamic-frames/dfcc.cpp	98.06% <100.00%> (ø)
...rc/goto-instrument/contracts/memory_predicates.cpp	84.57% <100.00%> (-0.40%)	⬇️
src/goto-instrument/stack_depth.cpp	100.00% <100.00%> (ø)
src/goto-programs/link_to_library.cpp	100.00% <100.00%> (ø)
src/goto-programs/slice_global_inits.cpp	92.98% <100.00%> (-0.67%)	⬇️
src/linking/static_lifetime_init.cpp	98.78% <100.00%> (+0.15%)	⬆️

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[peterschrammel]

lgtm

[kroening]

Would it be sensible to make it a precondition that the initialize function exists, as opposed to doing a silent no-op?

[tautschnig]

I have now changed the usage model according to your suggestion.