* Fix a few issues around opaque types as outputs

Slang and HLSL support opaque types (textures, buffers, samplers, etc.) as members of `struct`s, mutable local variables, function results, and `out`/`inout` parameters. GLSL and SPIR-V do not.

In order to translate Slang code over to GLSL/SPIR-V we use a variety of passes that seek to eliminate all of the above use cases and produce code that only uses opaque types in the limited ways that GLSL/SPIR-V allow. This change relates to the passes that deal with function results and `out`/`inout` parameters.

There are two basic changes here:

1. The `specializeResourceOutputs` pass was only dealing with resource (texture/buffer) types. This change updates it to process sampler types as well.

2. The sequencing of the passes made it possible that an opaque-typed local variable might be left around after `specializeResourceOutputs`, which would mean the code is still invalid for GLSL/SPIR-V. This change adds an additional SSA-formation pass which would eliminate any opaque-type local variables whose lifetimes were made simple enough by the optimizations.

Together these changes fix a problem-case user shader that was failing to compile for Vulkan.

* Update slang-emit.cpp

Fix typo 'reuslt'

* Update slang-emit.cpp

Comment change to re-trigger CI build.

Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>