perf(OpenGL): draw only the polydata primitives that own elements

[PaulHax]

Context

vtkOpenGLPolyDataMapper visits all six primitive helpers on every draw, including helpers with no elements. Thats slow.

Results

400 polys-only actors, 300 measured frames per run.

Metric	Before	After
Median render-call time	29.0 ms	23.8 ms

Changes

Record the active helpers in updateBufferObjects immediately after
buildBufferObjects, including when a subclass overrides buildBufferObjects.
Use that list in renderPieceDraw, retaining the element-count check for helpers
released between rebuilds.

Note: A subclass that replaces updateBufferObjects without calling the base
implementation will not populate the active list.

PR Checklist

• GitHub Actions CI passed: semantic-release commit messages, lint, and tests
• Test coverage added
• Documentation and TypeScript definitions are updated to match these changes