Radians vs degrees for SCAD trigonometric functions

Currently, our trig. functions work with radians but the reference implementation uses degrees. This can cause surprises as the SCAD file is interpreted incorrectly.

We can
- Introduce a breaking change and switch SCAD engine to work with degrees (rotation function already uses deg)
- Hide this behind a compatibility flag (problematic because we don't know when to enable OpenSCAD compat mode which is disabled by default)
- Introduce something like language pragma, that would allow setting this per-project but seems tricky in presence of use/imports (per-file).

Related to this, @julialongtin proposed exposing ImplicitCAD (or Implicits SCAD engine) version as SCAD variable which could potentially be used to guard breaking changes.