Add a project setting to control reflection filter mode

[Calinou]

The default is bilinear filtering as before, but nearest-neighbor filtering can now be chosen for a retro look.

This affects sky radiance map and ReflectionProbe specular light.

This also marks additional settings as requiring a restart, as noticed during testing.

• This closes https://github.com/godotengine/godot-proposals/issues/8063.

Testing project: test_reflection_nearest_neighbor.zip

Preview

Without ReflectionProbe

Linear

https://github.com/godotengine/godot/assets/180032/de5eb236-68eb-4024-8673-8e4d07e8474f

Nearest

https://github.com/godotengine/godot/assets/180032/5a63987c-d640-4aee-887c-36f59090cbc3

With ReflectionProbe

Linear

https://github.com/godotengine/godot/assets/180032/40af8661-37f8-4dd0-82da-7cc2529ff1ed

Nearest

https://github.com/godotengine/godot/assets/180032/27005638-57f3-40c0-adf8-e964f57c51b0

TODO

• [ ] Implement in Compatibility.
• [ ] Fix undefined uniform set error in Forward+ when SDFGI is enabled.