impr: Expand support for `generateMipmaps()` on TgpuTextures

[reczkok]

Currently the implementation only supports textures that are:

• 2d
• have a format that can be sampled as float or unfilterable-float

Since those are some pretty heavy restrictions we should expand it by:

• allowing for any texture dimension
• creating a compute pipeline downsampling implementation for textures that cannot be sampled

As a part of this task I would also measure the performance of downsampling using a sampler inside a fragment shader vs a compute shader implementation.