MTOH issues with lights intensity and wrong look

**Describe the bug**

I know this is not big of a deal since non of the maya lights are even close representation of an actual lighting but maybe in the future we will get some nice preview in the viewport so I am reporting this.

- Lights intensity is completely different than what VP2 is displaying.
- Arnold lights obviously are not working
- There is no penumbra causing the back light too look like black plane

**Steps to reproduce**
Steps to reproduce the behavior:
1. Switch to MTOH
2. Add some area lights

**Expected behavior**
Lights intensity closer to what we get in path tracer
Penumbra and Umbra - better representation of area lights

**Attachments**

**Specs (if applicable):**
- Windows 10
- Maya beta PR113

Start by reproducing the issue in MTOH with area lights, comparing the viewport result with VP2 and the path tracer. Check how MTOH handles Maya and Arnold lights, especially intensity, penumbra, and umbra. Done means area-light previews have closer intensity and visibly represent penumbra and umbra without the black-plane appearance.

Written by the indexing model from the issue text.