Add basic support for rotation mech

[freezy]

Mechs are a complex topic and this PR starts by splitting the former cannon component in two:

• A StepRotatorMechComponent, which simulates the mech
• A RotatorComponent which applies rotation on the playfield, inclusively balls.

The rotator component (documentation) works by introducing a new IRotatableComponent interface, which allows setting a z-rotation and retrieving the position on the playfield. One of those is the defined as the "target", and other objects can be added which will rotate around the target. Rotation is applied to the mesh, but also to other relevant attributes like the eject angle for kickers (however, colliders still cannot be moved). Balls in the kickers are correctly rotated as well.

It somewhat works now with a cannon, although there are many more changes needed in order to support more generic mechs.

https://user-images.githubusercontent.com/70426/139556198-e9eed966-0c88-4cf9-874f-f33de4137144.mp4

Other Changes

• Fixed a bug in teleporter
• Bumped Unity to 2021.2
• Removed obsolete angle/speed from kicker (it's handled by the coils array)
• Don't spam console when using ball roller with no ball
• Fixed a bug when an object sits on a ramp

TODO

• [x] Icons for rotation and step rotation components
• [x] Documentation for RotatorComponent

[codecov[bot]]

Codecov Report

Merging #337 (00b8a23) into master (e400379) will increase coverage by 0.47%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #337      +/-   ##
==========================================
+ Coverage   83.43%   83.90%   +0.47%     
==========================================
  Files         125      125              
  Lines        6736     6734       -2     
==========================================
+ Hits         5620     5650      +30     
+ Misses       1116     1084      -32     

Impacted Files	Coverage Δ
VisualPinball.Engine/VPT/Kicker/KickerData.cs	82.85% <ø> (+7.18%)	:arrow_up:
...isualPinball.Engine/VPT/Primitive/PrimitiveData.cs	81.18% <0.00%> (+1.48%)	:arrow_up:
VisualPinball.Engine/VPT/Surface/SurfaceData.cs	88.00% <0.00%> (+6.00%)	:arrow_up:
VisualPinball.Engine/VPT/Bumper/BumperData.cs	87.23% <0.00%> (+6.38%)	:arrow_up:
VisualPinball.Engine/IO/BiffData.cs	94.85% <0.00%> (+14.70%)	:arrow_up:

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