Style: Enforce separation line between function definitions

I couldn't find a tool that enforces it, so I went the manual route:
```
find -name "thirdparty" -prune \
  -o -name "*.cpp" -o -name "*.h" -o -name "*.m" -o -name "*.mm" \
  -o -name "*.glsl" > files
perl -0777 -pi -e 's/\n}\n([^#])/\n}\n\n\1/g' $(cat files)
misc/scripts/fix_style.sh -c
```

This adds a newline after all `}` on the first column, unless they
are followed by `#` (typically `#endif`). This leads to having lots
of places with two lines between function/class definitions, but
clang-format then fixes it as we enforce max one line of separation.

This doesn't fix potential occurrences of function definitions which
are indented (e.g. for a helper class defined in a .cpp), but it's
better than nothing. Also can't be made to run easily on CI/hooks so
we'll have to be careful with new code.

Part of #33027.

core/math/transform.h

@@ -117,6 +117,7 @@ _FORCE_INLINE_ Vector3 Transform::xform(const Vector3 &p_vector) const {
 			basis[1].dot(p_vector) + origin.y,
 			basis[2].dot(p_vector) + origin.z);
 }
+
 _FORCE_INLINE_ Vector3 Transform::xform_inv(const Vector3 &p_vector) const {
 	Vector3 v = p_vector - origin;
 
@@ -138,6 +139,7 @@ _FORCE_INLINE_ Plane Transform::xform(const Plane &p_plane) const {
 
 	return Plane(normal, d);
 }
+
 _FORCE_INLINE_ Plane Transform::xform_inv(const Plane &p_plane) const {
 	Vector3 point = p_plane.normal * p_plane.d;
 	Vector3 point_dir = point + p_plane.normal;