asm: support sampler and as types

[msiglreith]

Sampler and Acceleration Structure types should get a definition as well when used in an asm! block.
Otherwise, it triggers an ICE down the line e.g as element type of a runtime array:

thread 'rustc' panicked at 'Tried to lookup value that wasn't a type, or has no definition',
E:\Desktop\rust-gpu\crates\rustc_codegen_spirv\src\spirv_type.rs:199:22