deprecate source_locationt::get/set_function

[kroening]

Following #2149, this deprecates source_locationt::get/set_function; the reason is given as a comment.

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[tautschnig]

Well, yes, I'm all for it, but then we need to make progress on #3514 to demonstrate that this removal is actually doable.

[tautschnig]

Well, yes, I'm all for it, but then we need to make progress on #3514 to demonstrate that this removal is actually doable.

Which, in turn, means that we need to revive #4131 and get clarity on that.

[kroening]

I am aware; this PR is to be seen as deterrent for new usage.

[tautschnig]

I am aware; this PR is to be seen as deterrent for new usage.

I can see that this might work for get_function(), but usage of set_function() may be required because of other, existing functionality (such as labelling properties).

[codecov]

Codecov Report

Base: 77.99% // Head: 77.99% // No change to project coverage 👍

Coverage data is based on head (99ce20c) compared to base (9baef8f).
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #7239   +/-   ##
========================================
  Coverage    77.99%   77.99%           
========================================
  Files         1619     1619           
  Lines       187184   187184           
========================================
  Hits        145999   145999           
  Misses       41185    41185           

Impacted Files	Coverage Δ
src/util/source_location.h	100.00% <ø> (ø)

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