A number of headers in the codebase included `rendering_server.h` just for
some enum definitions. This means that any change to `rendering_server.h` or
one of its dependencies would trigger a massive incremental rebuild.
With this change, we decouple a number of classes from `rendering_server.h`,
greatly speeding up incremental rebuilds for that area.
On my machine, this reduces incremental compilation time after an edit of
`rendering_server.h` by 60s (from 2m57s).
Masses in Godot are specified in kilograms.
This also fixes the SoftBody3D mass being limited to increments of 1 kg,
now allowing adjustments to the nearest gram.
Previously, if you pinned a point by clicking on one of the soft body
vertex handles, the scene was not marked as modified, and the action
could not be undone by hitting Ctrl + Z.
Co-authored-by: Tomasz Chabora <kobewi4e@gmail.com>
