Check if depth is filterable in SSR and PCSS

[beicause]

Objective

Fixes #23965, Fixes #23977

Solution

Check if depth is filterable instead of #[cfg(not(target_arch = "wasm32"))] in SSR, and if not, disable PCSS.

Also replace the linear sampling emulation with a more effecient method via one textureGather.

TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES feature is removed from default wgpu settings, to make the settings respect WGPU_SETTINGS_PRIO="webgpu".

Testing

WGPU_SETTINGS_PRIO="webgpu" cargo r --example ssr --features bluenoise_texture
WGPU_SETTINGS_PRIO="webgpu" cargo r --example pcss --features experimental_pbr_pcss

The ssr example texture bindings (17) exceeds default webgpu limit (16). I disable ScreenSpaceAmbientOcclusion conditionally so it can run with webgpu limits.