drop forward renderer, focus on tiled one

[illwieckz]

It would be good to drop the forward renderer to not have to maintain two renderers. The tiled renderer seems to be the default for age, so it looks ok, and if there is issues in it, they must be fixed.

In #193 @cmf028 said there: #193 (comment)

The tiled lighting path is currently disabled when realtime shadows are enabled. To fix this, we need to render our shadows into a single tiled shadow map like Doom (2016) does so we can access it when we loop over the lights here.

This seems to be the only reason why people would look for the forward renderer today. In anyway realtime shadows are only good in screenshots, when they work, if they work. So I would not be against removing the option for them from preference dialog until we got them working on tiled renderer.

[slipher]

Following the old discussions on this, I did UnvanquishedAssets/unvanquished_src.dpkdir@c16b3b2 which prevents the r_dynamicLight cvar from being set to the value that causes the forward renderer to be used from the menu.

Are there other relevant cvars besides that?

ping

[illwieckz]

We need some wizard able to do that:

• implement realtime shadows that work on tiled renderer #242
• implement realtime sun light on tiled renderer #241

We can also drop the current implementation of them because it's now unused. I don't know how much of the current implementation can be reused though.

[slipher]

Duplicate of #747.