Fix interior sun direction (bug #7585)

Fixes #7585 (closed). Use the sun direction reverse-engineered by Hrnchamd inverted to be used as the sun position. This accounts for most of the visual difference observed in the issue report and also affects shader lighting. There are still some subtle brightness and light priority differences, but most users will never perceive them because they would use shader-based lighting system which is wildly different brightness-wise.

Note there are three options in each comparison.

• Caius Cosades' house COC destination
• Mournhold dummy cell
• Ald'ruhn's fighters guild (note .48 and Morrowind screenshots are from the report)

Note the tapestry is obviously more lit in the Morrowind screenshot for Caius Cosades' house. Legacy lighting appears to omit the candle light from the tapestry's light sources but shader lighting (not included in the comparison) appears to pick it up.