Improve DrawingTurtle position handling and visual bug fixes

[mstphayassin]

Please check if the PR fulfills these requirements:

• The commit message follows our guidelines.
• For bug fixes and features:
  • You tested the changes.

Close issues:

• Lesson 7, Practice 2 — Turtle animation not working as expected.  #597
• Practice 7.2 Drawing Squares at 3 positions #941
• Lesson 7.2 exercise #1062
• Ch 7 ex 2 : visual error with the moving turtle #888
• Lesson 7 Exercise 2 is completely broken. #968
• Lesson 7 Exercise 2 issue #958
• 7. 2. Jump Function Behavior Is Odd #1002
• Lesson 5.2 - Solution with 3 non-overlapping squares is not accepted #1043
• Lesson 19 : Rectangles do not overlap (but they do) #1114

The DrawingTurtle app has been reworked to detect when a user accesses and changes the position variable directly (this was unhandled before). This change fixes major visual bugs that occurred when users accessed both the position variable and used the jump function. It also properly detects when polygons are closed by checking if vertices are aligned. Now, polygons can be closed due to the jump() function, due to a change in the position variable, or when the polygon is actually closed.

I've gone through and tested each and every lesson which uses the DrawingTurtle app and ensured that the correct solutions all still work. However, I can't say that I've gone through and tested every permutation of every error message. I will need some help with that.

One other thing. I've noticed that the camera seems slightly less responsive now. I'm not sure why. I don't believe anything I changed should have affected the camera.

[mstphayassin]

Unfortunately, running integration_test_course.tscn results in exactly 1 test failed and 52 tests successful.

However, I don't believe the failed test has anything to do with these commits. I'm getting the same failure message on the latest version.

It has to do with Lesson 2 Practice 1 and does not involve the DrawingTurtle app whatsoever. It is described in issue #1173.