CMCL-0000: Camera selection bugfixes and various tweaks

[glabute]

Purpose of this PR

This is a bag with a bunch of small things.

A. Undo problem with child camera selectors in Sequencer and State Driven Camera:

1. Add some child cameras and some instructions
2. select the child cameras in the instructions
3. delete the child cameras
4. press undo/redo: the selectors don't update properly on redo

B. Add CinemachineVirtualCameraBaseEditor as default editors for CInemachineVirtualCameraBase, and make our custom inspectors inherit from it. This improves the quality of inspectors for client-authored cameras and managers (e.g. see the improved inspector for the custom CameraRig in the ThirdPersonWithAimMode sample).

C. Improved inspectors and user manual for CinemachineSplineRoll and LookAtTargetsOnSpline

D. Minor layout tweaks in inspectors: spacings and column alignment, mostly.

E. Added concept of State to SimplePlayerAnimator.cs in the sample code. This is not currently used, but is just future-proofing.

F: Minor tweaking of blend times (into and out of jumping) in the animation controller. This is part of the sample assets.

Testing status

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

Documentation status

• Updated CHANGELOG
• Updated README (if applicable)
• Commented all public classes, properties, and methods
• Updated user documentation

Technical risk

low

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 3.65854% with 79 lines in your changes missing coverage. Please review.

Project coverage is 26.96%. Comparing base (f38e9bd) to head (e5a39a9).
Report is 4 commits behind head on main.

Files	Patch %	Lines
...itor/Editors/CinemachineVirtualCameraBaseEditor.cs	0.00%	22 Missing ⚠️
...hine/Editor/Utility/CinemachineSceneToolHelpers.cs	0.00%	19 Missing ⚠️
...ditor/PropertyDrawers/ChildCameraPropertyDrawer.cs	0.00%	14 Missing ⚠️
...itor/Editors/CinemachineStateDrivenCameraEditor.cs	0.00%	6 Missing ⚠️
...Editor/Editors/CinemachineSequencerCameraEditor.cs	0.00%	4 Missing ⚠️
...itors/CinemachineSplineDollyLookAtTargetsEditor.cs	0.00%	4 Missing ⚠️
...hine/Editor/Editors/CinemachineSplineRollEditor.cs	0.00%	4 Missing ⚠️
...emachine/Editor/Editors/CinemachineCameraEditor.cs	0.00%	1 Missing ⚠️
...chine/Editor/Editors/CinemachineClearShotEditor.cs	0.00%	1 Missing ⚠️
...machine/Editor/Utility/CmCameraInspectorUtility.cs	0.00%	1 Missing ⚠️
... and 3 more

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1014   +/-   ##
=======================================
  Coverage   26.96%   26.96%           
=======================================
  Files         254      254           
  Lines       28419    28425    +6     
=======================================
+ Hits         7664     7666    +2     
- Misses      20755    20759    +4     

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[eakesy]

A. Reproduced issue on main branch with Sequencer and State Driven components. Confirmed fix for issues on both components. No additional issues found.
B. Compared CameraRig component the Inspector. Changes confirmed. No issues found.
C. Compared CinemachineSplineRoll and LookAtTargetsOnSpline components in the Inspector. Changes confirmed. No issues found.
D. Compared Cinemachine Camera component in the Inspector. No visible change. No issues found.
E. Verified all 3D Samples. Work as expected. No regression found.
F. Compared jumping in place, walking & running animations. No noticeable change. Jump transition looks smooth to me.
Conclusion: no issues found, tested all 3D Samples. Approved!