[Enhancement]: Increase shader cache size at default

### Problem / Motivation

Hey,

i personally think that the default shader cache size is with 1GB a bit to small nowadays for most users.
Yes it can be increased manually, but I think the default value should be set apart of it like 2G or even 4G on install. I personally think most users have enough space free for a little size increase.

relevant docs:
https://docs.mesa3d.org/envvars.html#envvar-MESA_SHADER_CACHE_MAX_SIZE
https://wiki.cachyos.org/configuration/gaming/#increase-maximum-shader-cache-size

Furthermore it is recommended to disable steams own pre-caching shader feature which then easily hits the limit.

### Proposed Solution

Set global environment with increased default value. The local user config in the docs should be still adjustable so that the user can increase/decrease it themnselves if needed.

### Alternatives Considered

_No response_

### Additional Context

_No response_