Rework pipeline shader spec info

[kevyuu]

Rework SShaderSpecInfo for ICPUPipeline to be more mutable:
IPipelineBase::SShaderSpecInfo should be templated on a boolean being mutable or not, such that members are conditional_t, and for CPU:

• shader is smart pointer
• entryPoint is a string and not a string view
• entries are an actual unordered_map instead of a pointer to one (this is bit complicated cause you need to make IPipelineBase::SShaderSpecInfo::SSpecConstantValue hold a vector of uint8_t instead of a const void* + size

[devshgraphicsprogramming]

Everything resolved, work continues in #887