Geometry Nodes: don't log full fields when not necessary

Previously, the field on every socket was logged for later use. This had
two main negative consequences:
* Increased memory usage, because the fields may contain a lot of data
under some circumstances (e.g. a Ray Cast field contains the target geometry).
* Decreased performance, because anonymous attributes could not be
removed from geometry automatically, because there were still fields that
referenced them.

Now most fields are not logged anymore. Only those that are viewed by a
spreadsheet and constant fields. The required inputs of a field are still
logged in string form to keep socket inspection working.

Geometry Nodes: support viewing field values in spreadsheet

The viewer node has been expanded to have a field input next to the
geometry input. When both are connected (by ctrl+shift clicking on a node)
the spreadsheet will show the evaluated field on the geometry.

The operator to link to the viewer has become a bit smarter. It automatically
detects if it should link to the geometry or field input. In the future some more
smartness could be added, such as automatically relinking the "right" geometry
when viewing a field.

Internally, there are two major changes:
* Refactor of what happens when ctrl+shift clicking on a node to link to
a viewer. The behavior of the geometry nodes viewer is a bit more complex
than that of the compositor viewers. The behavior in compositing nodes
should not have changed. Any change should be reported as a bug (and then
we can decide if it's worse than before or if it needs fixing).
* Evaluation, display and caching of fields in the spreadsheet editor.

Differential Revision: https://developer.blender.org/D12938

Fix T92460: crash when instancing on curves generated from string

Issue is that the Instance on Points node currently expects that all
instance references are used (see `remove_unused_references`).
This should be fixed at some point, but for now make sure that
the String to Curves node does not output unused references.

Fix: crash in previously added versioning code

Geometry Nodes: new Image Texture node

This adds a new image texture node for geometry nodes. It does not
reuse the same node that is used in shading, because we want to be
able to expose the image and frame as sockets.

There is a known update issue when a movie or image sequence is
used. That will be fixed separately (also see D12957).

Currently, the image socket is just a pointer to an Image ID data block.
This can contain single images but also movies and image sequences.
In the future, the definition of an image socket can be expanded to
include images that are generated from scratch in the node tree.
For more details read the discussion in D12827.

Some of the code is a direct port from cycles and should be cleaned
up a bit in the future. For example `image_cubic_texture_lookup`.

For still images, the frame input is ignored. Otherwise, the frame
has to be in a valid range for the node to work. In the future we
may add e.g. automatic looping functionality.

Differential Revision: https://developer.blender.org/D12827

Spreadsheet: fix updating active domain when component type changes

The mesh and instances case wasn't handled before.

Geometry Nodes: use vector socket for offset in Set Position node

This replaces the boolean Offset input in the Set Position node with
a vector input. This makes the node easier to use. Using a "Position"
input as an "Offset" sounds wrong anyway.

The Position and Offset inputs are evaluated at the same time.

The versioning only works correctly when the Offset input was not connected
to something else before.

Differential Revision: https://developer.blender.org/D12983

Fix T92446: node editor overlays reset automatically

Caused by rBcf72b10075758be971f9806b97db01f98383aba2.

The fix is to only enable the flags when a new node editor is actually created.

Fix: memory leak after type conversion in geometry nodes group

The leak happened when two things were true:
* Inside of a node group a socket is linked to a Group Input that has
a different type.
* The corresponding input on the parent Group node is not linked.

The conversion happened correctly, but the original value wasn't
destructed.

Cleanup: quiet asan warning because of uninitialized variable