Implement #82: Add an arc method

[PaulDance]

This is part of #82 by following the mentoring instructions. However, only the part 1 is covered in the current state, hence the draft. Part 2 will be implemented when the intermediate review is finished and adequate instructions completed.

Steps of the issue that have been covered:

• [x] Step 1: Add methods on Turtle called arc_left and arc_right that block on corresponding methods on AsyncTurtle.
• [x] Step 2: Add arc_left and arc_right asynchronous methods on AsyncTurtle that await on a new circular_arc method on ProtocolClient.
• [x] Step 3: Add the circular_arc method on ProtocolClient.
  • [x] Signature changed from issue: added the necessary TurtleId.
  • [x] Implementation with inscribed fixed-sized regular polygon approximation
  • [x] using the move_forward and rotate_in_place methods.
  • [ ] No changes to Radians.
• [x] Documentation
  • [x] Major points should be covered.
  • [x] Detailed examples with assertions.
• [x] New flower example illustrating arcs
• [x] using different pen sizes.
• [x] Abnormal cases are ignored: new tests cover that in turtle::tests::ignores_nan_inf_zero.
• [x] The methods are marked as "unstable".
• [x] Tests run fine.

The documentation looks like this for now:

As a general comment, the overall structure should be satisfying, it is quite simple after all. However, the current implementation interestingly performs very poorly: it is imprecise, very slow, laggy and gets worse over time. That could be caused by a mistake or just by the simplistic algorithm used that generates hundreds of IPC requests. Either way, it is definitely not the intended final state.

[codecov[bot]]

Codecov Report

Merging #206 into master will increase coverage by 0.70%. The diff coverage is 85.24%.

@@            Coverage Diff             @@
##           master     #206      +/-   ##
==========================================
+ Coverage   60.81%   61.51%   +0.70%     
==========================================
  Files          40       40              
  Lines        2636     2697      +61     
==========================================
+ Hits         1603     1659      +56     
- Misses       1033     1038       +5     

Impacted Files	Coverage Δ
src/async_turtle.rs	77.77% <62.50%> (-1.79%)	:arrow_down:
src/ipc_protocol/protocol.rs	55.33% <66.66%> (+0.51%)	:arrow_up:
src/turtle.rs	92.56% <100.00%> (+2.27%)	:arrow_up:
src/point.rs	58.82% <0.00%> (+2.94%)	:arrow_up:

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[sunjay]

Please also rebase this branch when you get a chance. :)