CMCL-0000: Scene view tools cleanup

[glabute]

Purpose of this PR

Scene view tools was overly complicated to support CM's old hidden game object architecture.
This PR removes all that and simplifies the code.

Scene view tools should work exactly the same as before.
Legacy CM2 components no longer support scene view tools.

Testing status

• Added an automated test
• Passed all automated tests
• Manually tested

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 1.30719% with 151 lines in your changes are missing coverage. Please review.

Project coverage is 26.90%. Comparing base (cedfb6c) to head (3c04541).
Report is 3 commits behind head on main.

Files	Patch %	Lines
...e/Editor/Editors/CinemachineOrbitalFollowEditor.cs	0.00%	60 Missing ⚠️
...ditor/Editors/CinemachinePositionComposerEditor.cs	0.00%	20 Missing ⚠️
...itor/Editors/CinemachineThirdPersonFollowEditor.cs	0.00%	20 Missing ⚠️
...emachine/Editor/Editors/CinemachineCameraEditor.cs	11.11%	16 Missing ⚠️
...emachine/Editor/Editors/CinemachineFollowEditor.cs	0.00%	8 Missing ⚠️
...hine/Editor/Editors/CinemachineHardLookAtEditor.cs	0.00%	8 Missing ⚠️
...ditor/Editors/CinemachineRotationComposerEditor.cs	0.00%	8 Missing ⚠️
...ity.cinemachine/Editor/Obsolete/CinemachineTool.cs	0.00%	5 Missing ⚠️
...hine/Editor/Editors/CinemachineSplineRollEditor.cs	0.00%	3 Missing ⚠️
...hine/Editor/Utility/CinemachineSceneToolHelpers.cs	0.00%	3 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1003      +/-   ##
==========================================
+ Coverage   26.80%   26.90%   +0.10%     
==========================================
  Files         249      249              
  Lines       28215    27950     -265     
==========================================
- Hits         7562     7520      -42     
+ Misses      20653    20430     -223     

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[AntoineCharton]

[AntoineCharton]

Just wait to see if the doc is green but the feature works.