This patch will make use of the eDrawType where it was used as a
variable or parameter name. The eObjectDrawType was renamed to eDrawType
as it is also used by `View3DShading.type`.
Motivation the functions get 3 different kind of flag parameters (ImBuf,
DrawType, OffscreenRendering) the naming of the flags were not clear,
leading to mistakes and unnecessary time spend debugging.
