[NUI][API12] Keep DRGLView delegate at least 1 frame rendering

[NUI][API12] Keep DRGLView delegate at least 1 frame rendering

Backport patch for #6775 and #6826

Keep CustomAlphaFunction's delegate at least 1 frame

Let we collect all custom alpha functor when we all Animate() API.

If we call Clear() or Animation become Dispose(), let we move those
delegates reference to some global static holder, named `RenderThreadObjectHolder`.

The `RenderThreadObjectHolder` will clear the items after at least 1 frame updated.

We determine the frame updated by the Animation's finished callback.

Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>
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Keep DRGLView delegate at least 1 frame rendering

Since DRGLView's rendering callback invoked at render thread,
we need to keep those delegate at least 1 frame until those
delegate will never be called at native side.

We have good internal class for this case, named `RenderThreadObjectHolder`.

Signed-off-by: Eunki Hong <eunkiki.hong@samsung.com>