Fix various errors in the class reference

[timothyqiu]

Found several errors when translating the class reference:

• Entries displayed in the inspector are properties, not variables.
• The description of LabelSettings.stacked_shadow_count is written as if it's a method.
• Control._get_drag_data(): we should be considering drag position instead of drop position.
• Typos like Linux (X11/Linux), ID capitalization and duplicated words.
• Unnecessary mention of enum types in FoldableContainer properties.
• Unnecessary difference between CPUParticle{2D,3D}.set_particle_flag() descriptions.

[Mickeon]

• Unnecessary difference between CPUParticle{2D,3D}.set_particle_flag() descriptions.

See also the more extensive (please it's in limbo for little reason)

• Fix differences between CPUParticles2D and CPUParticles3D documentation #104354

[akien-mga]

Thanks!