Blender Git Loki

Fix T88433: no greaspencil depsgraph evaluation with certain drivers

When the same stroke was used as a driver variable, this could make this
stroke already tagged as built in the course of building driver
variables (via `build_gpencil`), but then important stuff from
`build_object_data_geometry_datablock` could be missed later on (because
both of these funtions use `checkIsBuiltAndTag`). Most importantly,
setting up operations such as GEOMETRY_EVAL would be skipped entirely.

`build_object_data_geometry_datablock` seems to cover greasepencil just
fine (does the same as `build_gpencil` and more). Proposed solution is to
remove `build_gpencil` entirely. In `build_id` it would then also call
`build_object_data_geometry_datablock` for `ID_GD` IDs. Now the covered
types that _call_ `build_object_data_geometry_datablock` match exactly
to what is covered _inside_ `build_object_data_geometry_datablock`.

Think this "duplication" of functionality was just overseen in
rB66da2f537ae8 [`build_gpencil` existed long before and said commit made
greasepencil a real object with geometry and such].

thx @JacquesLucke for additional input!

Maniphest Tasks: T88433

Differential Revision: https://developer.blender.org/D12324