Make spvBinaryToText() independent of context and env

Currently, it seems one must do the following to get SPIR-V disassembled:

```
spv_context context = spvContextCreate(SPV_ENV_UNIVERSAL_1_3); // what env to use?
spvBinaryToText(context, ...
```

A SPIR-V binary stands alone, with no side-band environment information needed to understand it.

Hence, I would worry if `spvBinaryToText()` behavior is dependent on `context` that something might be wrong, but if not then it would be irrelevant.

So, it seems this parameter should not be present, and indeed, an independent consumer of SPIRV-Tools like glslang does not really know how to come up with an `env` enumerant.

Can this dependency be removed?

Start by locating the declaration, implementation, and callers of spvBinaryToText(), then inspect how its spv_context parameter affects disassembly. Check the API usage from the issue, including the glslang integration if available; done means the function no longer requires environment context and existing callers still build and behave correctly.

Written by the indexing model from the issue text.