refactor: ellipse rasterizer

[marco-langer]

Description

This PR implements some of the mentioned issues in my other comment regarding the ellipse rasterizer, namely:

• renamed midpoint_elliptical_rasterizer to midpoint_ellipse_rasterizer
• replaced colour vector with pixel type
• replaced std::array with point type for center and semi-axis
• removed unnecessary deep copies of temporaries.
• removed printing warnings to cout

There are still some open questions, e.g. why circle/line and ellipse rasterizer have different signedness for point types and why they implement the call operator differently. However, I am not sure if we are able to find any consensus on these topics before the deadline for Boost 1.80.

Tasklist

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

[codecov[bot]]

Codecov Report

Merging #692 (7279ffa) into develop (151fd9c) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #692   +/-   ##
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  Coverage    80.32%   80.32%           
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  Files          117      117           
  Lines         5032     5032           
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  Hits          4042     4042           
  Misses         990      990