feat: added apply_rasterizer() free function

[marco-langer]

Description

This PR implements the gil::apply_rasterizer() free function mentioned in #680.

However, I had to change the API of all three rasterizers quite considerably in order to squeeze them through this common interface. I am not sure if all those API changes are still debatable if we consider the deadline for Boost 1.80 in three days on 29th of June.

If you look at the updated examples, the usability is improved considerable (in my opinion) and it is still worth it (in my opinion) to discuss the PR, but I also understand that it might be too late for these kind of major API changes.

References

680

Tasklist

• [x] Ensure all CI builds pass
• [x] Review and approve

[codecov[bot]]

Codecov Report

Merging #695 (0fd05dc) into develop (adddbec) will increase coverage by 0.05%. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #695      +/-   ##
===========================================
+ Coverage    80.69%   80.75%   +0.05%     
===========================================
  Files          116      116              
  Lines         5072     5086      +14     
===========================================
+ Hits          4093     4107      +14     
  Misses         979      979              

[mloskot]

I am not sure if all those API changes are still debatable if we consider the deadline for Boost 1.80 in three days on 29th of June.

The rasterizers have not been released yet, so we are not breaking anything, IMO.