Blender Git Loki

alembic, cleanup, use the socket API to set the current frame and check
for precreated data

encapsulate AlembicObject's data

alembic, use min/max time sampling time to derive the frame index

alembic, avoid clearing the mesh, reload deleted data from previous
playback

cleaunp the procedural synchronisation a bit

rename Procedural::create, Procedural::generate

modify macros to avoid copying the arrays

use getters and setters for the Camera

use getters and setters for Background

use getters and setters for Light

add macros to define getters and setters

use getters and setters for Object

use getters and setters for Film

Removes Film::modified and several calls to Film::tag_update, and adds a
few more sockets.

use getters and setters for Shader

some notes:
- needs some for members only used in Cycles as well
- check usages of tag_update and need_update_geometry
- pass_id is now a socket

use getters and setters for the Integrator

Cycles: add update flags to Node and SocketType

Those flags are meant for detecting which socket has changed, so in the
future we can have more granular updates.

`Node` now stores an `update_flags` member which is modified every time
a socket is changed though `Node::set`. The flags are or-able bits
stored in `SocketType` instances. Each `SocketType` stores a unique bit
out of 32, for the 32 bits of an unsigned integer type; the bit
corresponds to the index of the socket in the `Node`'s sockets array +
1, so the socket at index 5 will have the 6th bit set as its flag. This
limits us to 32 sockets per Node, which should be plenty for the current
set of `Nodes` that we have.

This does not change the behavior of other parts of Cycles.

This is part of T79131.

Maniphest Tasks: T79131

Differential Revision: https://developer.blender.org/D8644

add alembic procedural code

start refactoring the Geometry nodes to make use of the getters and setters