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_2d.cpp

@@ -123,15 +123,18 @@ void Transform2D::scale(const Size2 &p_scale) {
 	scale_basis(p_scale);
 	elements[2] *= p_scale;
 }
+
 void Transform2D::scale_basis(const Size2 &p_scale) {
 	elements[0][0] *= p_scale.x;
 	elements[0][1] *= p_scale.y;
 	elements[1][0] *= p_scale.x;
 	elements[1][1] *= p_scale.y;
 }
+
 void Transform2D::translate(real_t p_tx, real_t p_ty) {
 	translate(Vector2(p_tx, p_ty));
 }
+
 void Transform2D::translate(const Vector2 &p_translation) {
 	elements[2] += basis_xform(p_translation);
 }