Light potion causes performance issues on lava level

[Bumber64]

Describe the bug
The light potion increases the radius of all light sources. This includes lava, which the lava level is full of. This can have a noticeable impact on game performance.

To Reproduce

1. Stand in an area with lots of lava (e.g., near obsidian dungeon entrance).
2. Drink light potion.
3. Performance suffers (including in inventory) causing delayed sound effects, etc.

Expected behavior
Maybe resolve in #695? Could also change light potion to exempt lava or just create light around the player.

Desktop

• OS: Windows 8.1
• Game version: 2.3.0-dev2