[mlir][spirv] Make SPIRVTypeConverter target environment aware

Non-32-bit scalar types requires special hardware support that may
not exist on all Vulkan-capable GPUs. This is reflected as non-32-bit
scalar types require special capabilities or extensions to be used.
This commit makes SPIRVTypeConverter target environment aware so
that it can properly convert standard types to what is accepted on
the target environment.

Right now if a scalar type bitwidth is not supported in the target
environment, we use 32-bit unconditionally. This requires Vulkan
runtime to also feed in data with a matched bitwidth and layout,
especially for interface types. The Vulkan runtime can do that by
inspecting the SPIR-V module. Longer term, we might want to introduce
a way to control how such case are handled and explicitly fail
if wanted.

Differential Revision: https://reviews.llvm.org/D76244