Two places that were not ready for GPv3:
- armatures were not set to posemode when entering weightpaint
- armatures were not in the object list when OpenGL selecting (thus
their bones were missing)
Both of them because existing code only respected
`eModifierType_Armature` (and not `eModifierType_GreasePencilArmature`
as well).
This is now corrected.
Similar to bdfb3ea6e7
Pull Request: https://projects.blender.org/blender/blender/pulls/130908
1448967287