Feature: Function parameters init as variables

[mrLSD]

Description

⏲️ Currently, function parameters are not interpreted as variables, and it means that Codegen should operate with that to the own choice.

mrLSD/toy-codegen explicitly shows, that it's a bit complicated, to operate with no pre-init variables, and has inner pitfalls with implementation for Codegen.

🕺 Proposal

Add function parameters as variables to BlockState, and add instructions to allocate and bind explicitly. As the solution: just use SemanticStackContext::LetBinding to fulfill SemanticStack result.