This patch reimplements the image partial updates. Biggest design motivation for the redesign
is that currently GPUTextures must be owned by the image. This reduces flexibility and adds
complexity to a single component especially when we want to have different structures.
The new design is not limited to GPUTextures and can also be used by reducing overhead in image
operations like scaling. Or partial image updating in Cycles.
The usecase in hand is that we want to support virtual images in the image editor so we can
work with images that don't fit in a single GPUTexture.
Using `BKE_image_partial_update_mark_region` or `BKE_image_partial_update_mark_full_update`
a part of an image can be marked as dirty. These regions are stored per ImageTile (UDIM).
When a part of the code wants to receive partial changes it needs to construct a `PartialUpdateUser`
by calling `BKE_image_partial_update_create`. As long as this instance is kept alive the changes can
be received.
When a user wants to update its own data it will call `BKE_image_partial_update_collect_changes`
This will collect the changes since the last time the user called this function. When the partial changes
are available the partial change can be read by calling `BKE_image_partial_update_get_next_change`
It can happen that the introduced mechanism doesn't have the data anymore to construct the
changes since the last time a PartialUpdateUser requested it. In this case it will get a request
to perform a full update.
Maniphest Tasks: T92613
Differential Revision: https://developer.blender.org/D13238
Currently there are many function declarations in `BKE_node.h` that
don't actually have implementations in blenkernel. This commit moves
the declarations to `NOD_composite.h`, `NOD_texture.h`, and
`NOD_shader.h` instead. This helps to clarify the purpose of the
different modules.
Differential Revision: https://developer.blender.org/D13869
