Prepare DECL/DEAD construction with location

[tautschnig]

Add new constructors to code_{decl,dead}t that also take a location.
This will help avoid some *_nonconst() calls. To facilitate this,
an additional make_dead instruction builder is also needed (which just
mirrors what we already have for other instruction types).

• 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.

[kroening]

This has a subtle problem: the location isn't supposed to go into the _code member any more, but into the _source_location member.

[tautschnig]

This has a subtle problem: the location isn't supposed to go into the _code member any more, but into the _source_location member.

I suppose we need to document this somewhere? Perhaps, however, this PR makes for a simpler transition as all those places can be spotted more easily?

[codecov]

Codecov Report

Merging #6420 (c58a207) into develop (f6fa03c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #6420   +/-   ##
========================================
  Coverage    75.98%   75.98%           
========================================
  Files         1524     1524           
  Lines       164299   164299           
========================================
  Hits        124843   124843           
  Misses       39456    39456           

Impacted Files	Coverage Δ
src/goto-programs/goto_instruction_code.h	100.00% <ø> (ø)
src/goto-programs/goto_program.h	89.76% <100.00%> (ø)

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[kroening]

Sure, simply fix those two new constructors, and it's good to go!

[tautschnig]

Closing as the new constructors shouldn't be necessary as indicated in the discussion.