Allows preplaced actors to be rendered on map preview when saving the
map.
Also removes requirements for ResourceLayer in OpenRA.Game and moves it
to OpenRA.Mods.Common.
This is as FrozenUnderFog.TickRender queues an update to the screen map. If this is not processed in the same tick, this results in screen bounds for the frozen actor being 1 tick behind. By making ScreenMap TickRender, it ensures changes from both Tick and TickRender traits are processed, rather than just Tick traits.
The render bounds for an actor now include the area covered
by bibs, shadows, and any other widgets. In many cases this
area is much larger than we really want to consider for
tooltips and mouse selection.
An optional Margin is added to Selectable to support cases
like infantry, where we want the mouse area of the actor
to be larger than the drawn selection box.
Additionally, internally renamed VisualBounds to SelectionOverlayBounds to avoid confusion with RenderBounds.
This step was necessary to prevent actors with selectable area smaller than their graphics to be removed too early from ScreenMap even though part of the graphics should still be visible.
RA cruisers were a prime example, but to a lesser extent several other actors were affected as well.
This separation also serves as preparation to determine the final RenderBounds from multiple source bounds later, to fix the remaining ScreenMap issues (building 'bibs', aircraft shadows).
And check DistanceAboveTerrain instead of just vertical distance to upgrade
source.
This is necessary to avoid situations where an actor is technically on the right
vertical distance above/below ground, but not upgraded because it is located on a lower/higher terrain level than the upgrade source.
