[DMN Designer] Need Palette glyph/icon and Canvas shape for Decision Service

We need a new "Palette" icon and Canvas shape for "Decision Services".

See Table 1: DRD components in the DMN 1.2 Specification.

See also 6.2.5 Decision service for some narrative regarding the shape.

A Decision Service is represented in a DRD as rectangle with rounded corners, drawn with a heavy solid border.... the Decision Service SHALL be divided into two parts with a straight solid line.

We are currently adding support for the expanded form however we will also require (at some stage) a Palette glyph/icon and Canvas shape for the collapsed form too.