Implement proper WMO doodad lighting

[fallenoak]

In the retail client, static WMO doodads are lit differently depending on their location in WMO groups that are exterior or interior.

• Exterior group doodads are lit using standard overworld lighting
• Interior group doodads are lit using an ambient color value present in the MODD entry in the WMO root file, and (likely) a special sun direction specific to interior doodads

Currently, we're lighting all WMO doodads with the same light as the overworld. This makes for some jarring doodad appearances.

In order to get WMO doodads to look right in interior groups, we should pass the color information from the MODD entry down to the doodad when the doodad is being instantiated. This information should override values in the light manager--it's not dynamic, so there's no need to involve the light manager.

Progress

• Switch sun direction for M2s to use a uniform instead of a hardcoded value
• Support passing in lighting overrides to M2s when instantiating
• Determine approximate lighting logic to use for interior doodads (incl interior sun direction, how to blend ambient and diffuse light, etc)