Physical skeleton improvement and bug fixes

[Wapit1]

Rework of the physical bone that aim to fix currently open issues and
also improve the current Physical Bone by adding stability and control.

The current Physical Bone implementation was using the normal rigid
bodies and joints, and it worked well but became unstable if the
complexity of the skeleton is not trivial, for this reason the
Featherstone algorithm was implemented to allowing to have not only a
stable body but also full control of it.

It is now not only possible to create ragdolls of non-animated bodies,
but is also possible to control its movement by adding forces with the
motor_* methods.
You don't have to deal with complex force systems, but instead you can
control it by simply changing the motor target and/or velocity and some
other parameters from the editor.

It is now possible to create active ragdolls directly from script, or
for example to create a completely physical walking robot, or to have a
stable ragdoll with dumpers and springs.

Fixes godotengine#19002
Fixes godotengine#22823
Fixes godotengine#24968
Fixes godotengine#25564
Fixes godotengine#26618
Fixes godotengine#28707