GlDrawer: Define the behavior and usage guidelines for sticky footer in drawers

Problem

!2876 (merged) introduced an optional sticky footer property to the Drawer component. We need to define the footer usage and behavior guidelines.

Proposal

We need to answer such questions as:

• Should the actions in the drawer go in the header or footer, when and why?
• Should we use an overlap scrim above the sticky footer when content scrolls underneath it?